What Is SEO?

Updated by Miriam Ellis on July 13, 2023.

SEO stands for search engine optimization. SEO practitioners optimize websites, web pages and content for the purposes of ranking higher in search engines, like Google. SEO is a set of practices designed to improve the appearance, positioning, and usefulness of multiple types of content in the organic search results. This content can include web pages, video media, images, local business listings, and other assets. Because organic search is the top method via which people discover and access online content, utilizing SEO best practices is essential for ensuring that the digital content you publish can be found and chosen by the public, increasing your website’s organic traffic.

In order to understand how SEO works, it’s vital to have a basic understanding of how search engines work. Search engines use crawlers (also known as spiders or bots) to gather information across the internet to populate their big databases, called “indexes”. Crawlers begin from a known web page and then follow links from that page to other pages.

For example, if a page Google already indexed on Patagonia.com on the topic of used clothing features internal links to further pages on the site for used jackets, used hiking boots, and used flannel shirts, Google can crawl to those pages via the links provided. Meanwhile, if Patagonia’s main used clothing page links out to an article on TheGuardian.com about the negative impacts of fast fashion, Google can crawl from Patagonia to the news article via the link, thereby discovering that content and potentially indexing it.

The content of the discovered page, and the context of the links the crawler followed from Patagonia to The Guardian, help Google understand what the page is about and how it is relevant to all of the other pages within its index.

If you happen to be the journalist who wrote The Guardian article on fast fashion, the fact that a used outdoor clothing section of a large brand is linking to your piece is an indication to Google that there might be a relationship between the problems of fast fashion and the potential solution of buying used clothing instead of new clothing. These semantic relationships go far towards helping Google determine which results to show for each query they receive from the searching public.

Search engines’ success as businesses depends on the public finding search engine results to be relevant to their needs. The more links a search engine like Google finds pointing from a particular type of content to a particular resource, the more confident it becomes that the linked-to resource is relevant to certain search queries. The search engine then determines that this resource deserves to be ranked highly when people make those queries.

There are three main categories of SEO: on-page SEO, off-page SEO, and technical SEO, all of which combine to help search engines discover, crawl, index, understand, and rank your content, and this article will cover each of these topics.

A significant reason that SEO matters is because it helps online publishers appear within the results displayed by search engines. Search engines like Google and Bing each have their own methods of surfacing and formatting the content they display when a user enters a query into a search box, like this:

In response to a query like this, a search engine like Google can return a wide variety of results, Let’s look at and label some of the different types of results here:

1. Traditional Organic Results

Google’s most familiar results are the traditional organic results, which consist of links to website pages ranked in a particular order based on Google’s algorithms. Search engine algorithms are a set of formulae the search engine uses to determine the relevance of possible results to a user’s query. In the past, Google commonly returned a page of 10 organic results for each query, but now this number can vary widely, and the number of results will differ depending on whether the searcher is using a desktop computer, mobile phone, or other device. Traditional organic results look like this, with each entry having a title, description, link to the source, and other features like dates and additional links:

Bing’s traditional organic results look and function similarly to Google’s:

2. SERP Features

Beyond the traditional organic results, search engines can surface a variety of other displays which can be categorized under the umbrella term “SERP features”. There are many kinds of SERP features including but not limited to:

• Local pack results
• Google Business Profiles
• Knowledge panels
• Sitelinks
• Featured Snippets
• Image packs and image carousels
• Video packs
• People Also Ask features
• Related searches
• Plus additional SERP features for news results, hotel and travel results, shopping, FAQs, job listings, and more.

Local pack results display a list of local businesses for some queries:

Google Business Profiles feature a single local business for some queries:

Knowledge panels feature information about organizations, people, and places for some queries:

Sitelinks are links to additional pages within a website, can also appear as part of that site’s organic listing if the individual pages are strong enough or the search engine believes the individual pages are especially relevant to the user’s query, like this example of an organic listing for a retailer including links to its pages for women’s wear, men’s wear, used clothing and more:

There are at least four main types of results called "featured snippets", including carousels, lists, paragraphs, and tables. Videos and rarer double featured snippets are related features. To display featured snippets Google pulls content from web pages to summarize right within the SERPs, linking to the sources of the information.

Image packs and image carousels that link to their sources:

Video packs that link to their sources:

“People also ask” features summarize and link to further information based on queries that relate to the user’s original query:

“Related searches” features link to further sets of SERPs and can prompt users to expand their query to access related information:

There are also additional SERP features for news results, hotel and travel results, shopping, FAQs, job listings, and more. SEO is important because it influences what search engines surface for all of these results and features.

What SEO doesn’t influence is any SERP component that has been paid for by an advertiser. Paid search engine results can include ads stemming from the Google Ads program, like this example with its “sponsored” label:

And local business lead generation ads stemming from Google’s Local Services Ads program which are returned for some queries:

Any time a result is labeled “sponsored”, you’ll know it is a paid ad placement and not influenced by your SEO efforts, but nearly all of the other types of results search engines display are highly impacted by your optimization strategy.

Finally, it’s important to know that both Google and Bing are currently in the early stages of offering Artificial Intelligence-based content to searchers, as explored by Tom Capper on the Moz Blog. The degree to which AI content can be impacted by SEO is, as yet, unknown. For example, it’s clear that SEO is having some impact on Google’s Search Generative Experience (SGE) experiments because the content found in traditional local packs is being used to some extent in SGE responses to local queries, like this:

What is less clear at this time is any precise strategy for seeking inclusion in offerings like Google’s Bard or New Bing chat. Over time, if these products become popular with the public, part of the work of an SEO will be studying AI results and identifying methods for building a presence within these novel formats and likely also competing against them for visibility in the evolving SERPs.

While every SEO campaign can have unique goals, most online publishers are united in wanting to achieve some or all of the five following results from their investment in optimization:

1. More visibility in the SERPs

The majority of Google users stay within the first page of Google’s results to find an answer to their query and 75% will click on either the first or second result on the page. Because of this behavior, one major goal of SEO is to rank more highly in the results for more searches. The more visible your content is, the better its chances of being found and chosen by the public.

At this stage in your learning it’s important for you to know that website owners shouldn’t pursue the myth of #1 search engine rankings, because entities like Google will show different results to different users based on the location of their devices and even minor differences in the language of their queries. A better goal than being #1 is to be highly visible to your focus audience for your most important searches across multiple SERP styles and features.

2. More traffic to your website and other assets

When searchers reach your site via clicking on the organic SERPs, this is known as “traffic”. Whether the click-thru-rate (CTR) to your website pages from the SERPs impacts organic rankings in Google is a matter of ongoing controversy and debate in the SEO industry. Bing confirms that they use both CTR and bounce rate (how quickly people leave your web page after landing on it) as ranking factors. But though the precise details of search engine algorithms remain secret, it stands to reason that a goal of SEO work is to bring more traffic from the SERPs to your online assets.

3. Better quality traffic to your website and other assets

While winning a slew of traffic from the SERPs may, at first, sound like a dream come true to any site owner, it will typically only impact basic business goals if this traffic converts into sales or other key actions. For example, an independently-owned doughnut shop in San Francisco might achieve first page rankings in Google for sourdough doughnuts. It might go viral on social media for a funny or unusual marketing campaign and make it into mainstream news. It might receive national or even international traffic from these rankings and efforts, but when its product is only actually available to be purchased by customers in its city, most of this traffic will not convert to sales and may be only nominally supportive of the viability of the company.

Because of this, a better goal than hoping for lots of traffic to your digital assets is to use SEO to strategize on how to win the most qualified traffic for what you offer, because this will typically have the highest conversion rate. High quality organic traffic depends on search engines determining that your content is highly relevant for the queries you discover are most likely to result in conversions, whether your conversions are defined as sales, filling out forms, phone calls, leads, or even just customers spending more time on your website. You can access further learning on measuring traffic quality in this blog post tutorial by Adriana Stern.

4. Greater intelligibility to the public

One of the best things you can do in learning about SEO is to understand it as a form of customer service. Google rewards content that is useful to the public. In fact, their 2022 Helpful Content algorithm update largely focused on how they reward sites that make a habit of publishing content that is of true use to searchers. For decades, Google has urged site owners to create content for people rather than for search engines.

SEO can help your site be more intelligible, discoverable, and usable to its potential visitors. Optimization influences both what your content looks like when shown within the SERPs and what your content looks and behaves like when searchers click through to your digital assets. Providing good service and a great user experience to the public is one of the most practical reasons to invest in SEO.

5. Greater intelligibility to search engines

In order for search engines to feature and reward your content so that you can earn the visibility, traffic, and conversions you need, your website and other assets need to be intelligible to the crawlers/spiders/bots that entities like Google and Bing use to crawl and index digital content. This is achieved by multiple SEO efforts that can be broken down into:

• On-page SEO, which chiefly consists of how you optimize specific elements of a website page so that its contents are relevance are clear

• Technical SEO, which chiefly consists of managing the technical backend of your website so that it can be effectively crawled, indexed, and understood by search engines.

• Off-page SEO, which chiefly consists of how you earn links, citations, notice, and press from third parties, thereby building up the authority of your digital assets

Taken altogether, these three areas of SEO work to ensure that search engines can match your content to their perceived intent of searchers’ queries. The better search engines can understand your content, the better your chances of achieving high, broad, and highly-converting rankings. We’ll look into each of these three concepts more deeply next.

Optimizing your site generally involves three key focus areas: On-page, off-page and technical SEO.

On-page SEO is the practice of optimizing your website contents so search engines and humans can easily digest it. Technical SEO is any sufficient technical action undertaken with the intent of improving search results, usually through making your site function efficiently. Off-page SEO involves actions taken outside of your website to impact your rankings.

Together they combine to create a solid foundation to enable you to reach your target audience.

On-page SEO

Investing in SEO includes engaging in customer research, market research, and keyword research so that your content reflects the language real people use to search for whatever your website offers. The findings of your research can then be incorporated into your optimization of multiple elements of your website and its pages, including but not limited to:

• Domain names

• Page URLs

• Page titles

• Headers

• Alt text

• Images

• Videos

• Navigational

• Meta description tags

• Internal links

• Sitemaps

• The main body text of each page

For a complete tutorial on on-page SEO, read: The Beginner’s Guide to SEO.

Technical SEO

To ensure that your website can be properly indexed and crawled by search engines and properly used by people, technical SEO includes, but is not limited to, management of all of the following elements:

• Analytics setup

• Site crawling

• Indexing status

• Robots.txt status

• Canonicalization

• Internal link architecture design and management

• Coding

• Mobile-friendliness

• Cross browser rendering

• Page status codes

• Image compression

• Core Web Vitals status

• Page load/speed optimization

• Structured data

• JavaScript frameworks/rendering/pre-rendering

• Hreflang

• De-indexing

• Migrations

For a complete tutorial on technical SEO, read: The Professional’s Guide to SEO and you’ll also enjoy this popular Web Developer’s SEO Cheat Sheet.

Off-page SEO

To ensure that your digital assets achieve maximum visibility in the search engines, meet your goals for relevant traffic, and deliver the conversions you seek, off-page SEO can basically be defined as a practice for bringing attention to your content. Your options for pursuing this include, but aren’t limited to:

• Earning links and citations from high quality third-party sites via the merit of your content

• Managing link disavowal

• Proactively building links and citations from high quality third-party sites via outreach to those publications

• Engaging in a variety of forms of online promotion, including social media marketing, being featured as a guest on third-party blogs, podcasts, and vlogs

• Traditional PR, including writing press releases and building relationships with influencers

• For local businesses, creating local business profiles and building local unstructured citations

For a complete tutorial on off-page SEO, read: Off-Page SEO and if you are optimizing a local business website, read The Essential Local SEO Strategy Guide.

All of the above factors combine to influence how search engines understand and rank your website pages.

Over the past few decades, SEO professionals have made many ongoing efforts to identify as many of Google’s proprietary organic rankings factors as possible, and to attempt to organize them in the order by which they appear to influence rankings. The same has been done for search engines like Bing, and for some years, Moz conducted a major organic ranking factors survey as well as a local search ranking factors survey. A list of such factors could include, but not be limited to:

• On-page factors

• User behavior factors

• Link factors

• Core update factors

• Local guidelines factors

• Spam factors

There are also the elements known as Google’s E-E-A-T factors, which, while not considered traditional, direct ranking factors by many SEOs, are a set of principles which Google instructs its quality raters to evaluate in measuring search engine results quality. E-E-A-T factors can be defined as:

• Experience - Is published content based on the first hand-experience of its author? For example, if someone writes a review of a restaurant, did they demonstrably visit the place and try the food. Or, if an influencer is recommending a brand of shampoo, did they actually use it on their own hair?

• Expertise - Is published content created by someone who has become skilled in the subject they are covering? For your-money-or-your-life (YMYL) topics like medical information or financial advice, does the author have degrees, licenses, accreditations? For other categories of information, like do-it-yourself home repairs, has the author accrued practical, everyday expertise through demonstrable experience?

• Authoritativeness - Do third parties recognize the expertise of a source? Do established authoritative sites and people link to and cite the content in question, as in the case of a well-known food critic linking to their choice of the best Thai restaurant in Seattle, recognizing its expertise in this field.?

• Trustworthiness - Is content factual and accurate, are websites and transactions secure and built on the principles of good user experience (UX), is contact information accessible and true, are policies accessible and appropriate, and does public sentiment (like reviews) indicate that a business is above-board and legitimate? Google calls trustworthiness the most important of all the E–E-A-T factors.

The problem inherent in the task of trying to set in stone a list of factors which definitely have the most influence on organic rankings is that the SERPs have become so diverse and varied.

If your organization sells shoes, your SEO and marketing efforts will need to be different than those undertaken by a hotel, or an online gaming platform, or an architectural firm, or a software developer, because the SERPs will not only contain different components for each relevant query, but may also be somewhat or completely different for each searcher, based on their location. Meanwhile, what the public needs and how it behaves may be quite different, depending on the intent of their query.

As the myth of #1 search engine ranking faded into the past, the logic of realizing that one size simply doesn’t fit all in SEO ranking factors may have contributed to us seeing fewer surveys these days trying to assign impact to each individual factor.

Because of this maturation of the SEO industry that has arisen out of the tremendous diversification of the SERPs, a newer and better best practice has arisen: studying what the search engine is returning for your most important queries and then analyzing the top competitors for these terms.

Rather than looking for universal top ranking factors, research the types of media Google, Bing, or other entities are returning for your top keyword phrases. Do you see strong organic competitors? Featured snippets? Image packs? Video results? Local packs? How big of an inroad is AI making in your corner of Search at this point, and how will your organization respond to it?

Learn to conduct a good organic competitor audit, a good local competitor audit, and to track and understand the SERP features that Google is surfacing for your audience. Master the basics of on-page, off-page, and technical SEO and then look for ways not just to compete with the top results, but to differentiate your brand in the SERPs so that you stand out to real people as the best and most relevant resource for their queries.

Be wary of claims you may encounter of offers to make your company #1 in the organic SERPs, or sources that empirically state that they absolutely know what search engines’ top ranking factors are. Only the search engines have this information, and SEO is actually all about the ongoing study of this topic as search evolves across time. Your knowledge of SEO basics learned on sites like this and through the use of SEO tools, paired with your own experimentation in your particular market, will be your best teachers as to which factors and which strategies are meeting your goals for SERP visibility and maximum conversions.

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