What Is SEO?

SEO stands for Search Engine Optimization and helps search engines understand your website’s content and connect it with users by delivering relevant, valuable results based on their search queries.

The goal of SEO is to rank on the first page of search engine results pages (SERPs) for the most relevant and valuable keywords to your target demographic, driving qualified traffic to your site.

SEO is considered a digital marketing practice and can be applied to any website. It helps improve a site’s visibility on search engines like Google and Microsoft Bing. Whether your site promotes products, offers services, or shares expert knowledge on a specific topic, SEO can help drive traffic and increase online visibility.

The better visibility your pages have in search results, the more likely you are to be found and visited.

This introductory guide will explain in more detail what SEO is and what it entails in 2025.

Technology is constantly evolving, which means that websites – and the way they are structured – evolve. So do the devices we use to access search engines.

A web search can be voice activated and a click may be a tap on a mobile phone screen. Even the results we see from our search engine of choice may be summarized by artificial intelligence (AI).

We will explain all these different aspects of SEO as well as provide resources for your continued learning.

How is SEO different from SEM and PPC?

SEM and PPC are two other common terms you will read about often here on Search Engine Land and hear about in the larger search marketing community.

It can also be helpful to distinguish what SEO is from what it is not.

Here, we’ll explain the difference in terminologies, what these abbreviations mean and how they extend to different disciplines.

SEO vs. SEM

SEM stands for search engine marketing – or, as it is more commonly known, search marketing.

Search marketing is a type of digital marketing. It is an umbrella term for the combination of SEO and PPC (pay-per-click, e.g. Google Ads) activities that drive traffic via organic search and paid search, respectively.

So how do SEO and SEM differ? Technically they aren’t different – SEO is simply one-half of SEM:

• SEO: Driving organic results clicks from search engines.
• SEM: Driving organic and paid results clicks from search engines.
• PPC: Driving paid results clicks from search engines.

Here’s the best way to think about SEM, SEO and PPC:

Imagine SEM is a coin. SEO is one side of that coin. PPC is on the flip side.

SEO vs. PPC

PPC: stands for pay-per-click – a type of digital marketing where advertisers are charged whenever one of their ads gets clicked on.

Advertisers bid on specific keywords or phrases that they want their ads to appear for in the search engine results.

When a user searches for one of those keywords or phrases, the advertiser’s ad (paid listing) will appear among the top results.

So again, if we think of search marketing as a coin, SEO and PPC are two sides of the same coin:

• With PPC, the advertiser pays when a search user clicks their paid listing.
• With SEO the search result listing has not been directly paid for, though SEO is sold as a service and the process of optimizing pages and websites takes time and investment, so it is important to understand that organic search isn’t “free.”

Some people have debated “SEO vs. PPC” – which channel is more valuable or has a better return on investment (ROI). However, SEO and PPC are complementary digital marketing channels. Ideally, you should always choose both (as long as your budget allows it).

As we mentioned before, the terms SEM and PPC are used within the industry interchangeably. However, that isn’t the case here on Search Engine Land.

Whenever we mention “SEM,” it will be because we’re referring to both SEO (organic search) and PPC (paid search).

If you’re curious about the history behind how “SEM” came to mean “PPC” at the exclusion of SEO, you can dig deeper in these articles:

Why is SEO important?

SEO is a critical marketing channel.

• Organic search delivers 53% of all website traffic, according to a 2019 BrightEdge study.
• More than 8.5 billion searches happen every day on Google Search and Google owns 91% of the global search engine market.

With such incredible audience reach, there’s no surprise that in turn, the global SEO industry is forecast to reach a staggering $122.11 billion by 2028.

SEO drives real business results for brands, businesses and organizations of all sizes. This is because the act of searching, or the search user interface (be it a typed, voiced or image query format) has become second nature for internet users worldwide, as the primary way to access the information sought, within the sea of billions of webpages (4.3 billion pages on the indexed web, as of September 2024).

Whenever people want to go somewhere, do something, find information, research or buy a product/service – their journey typically begins with a search.

However, search is incredibly fragmented – particularly for consumer-intent activities. Users may search on traditional web search engines (e.g., Google, Microsoft Bing), social platforms (e.g., YouTube, TikTok) or retailer websites (e.g., Amazon).

In fact, last year 56% of U.S. online shoppers started their product search on Amazon, compared to 46% who started on a search engine like Google. Also of note from that same research: 

• 37% start on Walmart.
• 25% start on YouTube.
• 20% start on Facebook.
• 19% start on Instagram.
• 19% start on TikTok.

Types of SEO and specializations

Imagine SEO as a sports team. To win, you need a strong offense and defense. But you also need fans (an audience).

Think of technical optimization as your defense, content optimization as your offense, and off-site optimization as ways to attract, engage and retain a loyal fanbase:

• Technical SEO: Optimizing the technical aspects of a website.
• On-site SEO: Optimizing the content on a website for users and search engines.
• Off-site SEO: Creating brand assets (e.g., ​​people, marks, values, vision, slogans, catchphrases, colors) and doing things that will ultimately enhance brand awareness and recognition (i.e., demonstrating and growing its expertise, authority and trustworthiness) and demand generation.

You maintain 100% control over content and technical optimizations. That’s not always true with off-site (you can’t control links from other sites or if platforms you rely on end up shutting down or making a major change), but those activities are still a key part of this SEO trinity of success. 

Technical optimization (technical SEO)

Optimizing the technical elements of a website is crucial and fundamental for SEO success.

It all starts with architecture – creating a website that can be crawled and indexed by search engines. As Gary Illyes, Google’s trends analyst, once put it in a Reddit AMA: “MAKE THAT DAMN SITE CRAWLABLE.”

You want to make it easy for search engines to discover and access all of the content on your pages (i.e., text, images, videos). Key technical elements include URL structure, navigation and internal linking.

User experience is another critical part of technical optimization. Search engines stress the importance of pages that load quickly and provide a good page experience. Elements such as Core Web Vitals, mobile-friendliness and usability, HTTPS and avoiding intrusive interstitials all matter in technical SEO. 

Another area of technical optimization is structured data (a.k.a., schema). Adding this code to your website can help search engines better understand your content and enhance your appearance in the search results. 

Plus, web hosting services, CMS (content management system) and site security all play a role in SEO. 

Content optimization (on-page SEO)

In SEO, your content needs to be optimized for two primary audiences: people and search engines. This means optimizing the content your audience will see (what’s actually on the page) as well as what search engines will see (the code).

The goal is always to publish helpful, high-quality content. You can do this through a combination of understanding your audience’s wants and needs, data and Google’s guidance.

When optimizing content for people, you should make sure it:

• Covers relevant topics with which you have experience or expertise.
• Includes keywords people would use to find the content.
• Is unique or original.
• Is well-written and free of grammatical and spelling errors.
• Is up to date, containing accurate information.
• Includes multimedia (e.g., images, videos).
• Is better than your SERP competitors.
• Is readable – structured to make it easy for people to understand the information you’re sharing (think: subheadings, paragraph length, use bolding/italics, ordered/unordered lists, reading level, etc.).

For search engines, some key content elements to optimize for are:

• Title tags
• Meta description
• Header tags (H1-H6)
• Image alt text
• Open graph metadata

Generative engine optimization (GEO) is an emerging specialty within content optimization. GEO is about optimizing your content for visibility in AI-driven search engines (or answer engines) including Google’s AI Overviews and Gemini, OpenAI’s ChatGPT and SearchGPT, Microsoft Copilot and Perplexity.

How does SEO work?

If you found this page via Google, you likely searched for something along the lines of [what is seo?]

This guide is published on Search Engine Land, an authoritative website with expertise and experience in SEO topics (we’ve been covering all SEO changes, big and small, since 2006). 

Originally published in 2010, this What is SEO page has earned hundreds of thousands of links.

Put simply, these factors (and others) have helped this guide earn a good reputation with search engines, which has helped it rank in a top 1-3 organic search position in most search engines, for a number of years. It has accumulated signals that demonstrate it is authoritative and trustworthy – and therefore deserves to rank when someone searches for SEO. 

But let’s look at SEO more broadly. As a whole, SEO really works through a combination of:

• People: The person or team responsible for doing or ensuring that the strategic, tactical and operational SEO work is completed.
• Processes: The actions taken to make the work more efficient.
• Technology: The platforms and tools used.
• Activities: The end product, or output.

Many other things factor into how SEO works. What follows is a high-level look at the most important knowledge and process elements. 

Six critical areas, in combination, make SEO work: