Search Engine Optimization (SEO) is the practice of improving a website so that it appears higher in the organic (unpaid) results of search engines like Google and Bing, and, increasingly, so that it is cited inside the AI-generated answers those engines now show. Higher visibility means more clicks, more visitors, and more of whatever your site exists to do: sales, signups, readers, leads.
Why SEO still matters#
Search is still the largest source of trackable web traffic for most industries. A few realities worth internalizing before you write a single line of code:
- Position decides traffic. Backlinko's analysis of 4 million results (2019, before AI Overviews) found the #1 organic result was about 10x more likely to be clicked than #10. The exact numbers have shifted since, but the shape of the curve has not: page two might as well not exist.
- Intent is built in. Someone searching "buy ergonomic chair" told you exactly what they want. No ad targeting can match that signal quality.
- It compounds. Content that ranks keeps producing traffic for years with near-zero marginal cost, unlike ads, which stop the moment you stop paying.
- Google still dwarfs AI assistants as a traffic source. Ahrefs found AI assistants sent about 0.1% of referral traffic across ~35,000 sites in March 2025, with Google sending roughly 345x more than ChatGPT, Gemini and Perplexity combined. Conductor's benchmark (published November 2025) put AI referrals at about 1% of all website visits. Growing fast, but still small.
The SERP has changed#
What has changed is how much of the answer happens on Google itself.
- AI answers are mainstream. Google reported in May 2026 that AI Overviews have over 2.5 billion monthly users and that AI Mode, its conversational search mode, passed 1 billion monthly users within a year of launch.
- Fewer searches end in a click. SparkToro's clickstream study of US searches (January to April 2026) found 68% of Google searches ended without a click to any website, up from about 60% in its 2024 study. The two studies used different data panels, so treat the comparison as directional.
- The way in is the same. Google says its AI features are "rooted in" its core ranking and quality systems and need no special files or markup. The pages that get cited are, overwhelmingly, pages that are already indexed and ranking well.
That's why this curriculum covers AEO and GEO too, and why it treats them as extensions of SEO, not replacements. SEO for AI Mode & AI Overviews covers Google's AI surfaces specifically.
The three pillars#
Almost everything in SEO falls into one of three buckets:
| Pillar | What it covers | Where to learn it |
|---|---|---|
| On-page | Content, titles, headings, internal links: everything on your pages | On-Page SEO |
| Technical | Crawlability, indexing, speed, structured data: how machines read your site | Technical SEO |
| Off-page | Links, mentions, reputation: signals from the rest of the web | Off-Page SEO |
A site needs all three. Brilliant content on an uncrawlable site is invisible; a technically perfect site with thin content has nothing to rank.
SEO vs. AEO vs. GEO#
The terms you'll see throughout these docs:
- SEO targets the classic ranked list of results. Goal: rank.
- AEO (Answer Engine Optimization) targets answer surfaces: featured snippets, People Also Ask, voice and multimodal assistants. Goal: be the answer.
- GEO (Generative Engine Optimization) targets AI systems that synthesize answers and cite sources: Google AI Overviews and AI Mode, ChatGPT search, Perplexity, Microsoft Copilot, Claude. Goal: be cited.
AEO and GEO are industry labels, not Google terms. Google's own guide to its generative AI features (May 2026) says standard SEO best practices apply and spends a section myth-busting "AEO/GEO" tactics such as special AI text files and chopping content into tiny chunks. In practice they share one foundation: crawlable, fast, well-structured, genuinely useful content. Master SEO and most of AEO and GEO becomes refinement, not reinvention. Look up any unfamiliar term in the SEO Glossary.
What SEO is not#
Modern SEO is closer to product work than to marketing hacks. The mental model that will serve you for the rest of this curriculum:
Search engines make money by giving people the best answer. Your job is to be the best answer, then remove every obstacle preventing machines from recognizing it.
How this curriculum is organized#
- Foundations (you are here): how search engines actually work, the tools, and the quality bar.
- Keyword Research: finding queries worth winning.
- On-Page and Technical SEO: building pages that rank.
- Off-Page SEO: earning authority.
- AEO and GEO: winning answers and AI citations.
- Platforms: visibility beyond your own site, on YouTube, Reddit and forums and Google Discover.
- Expert Practice: audits, programmatic SEO, migrations, forecasting, and a capstone audit of your own site.
Next up: How Search Engines Work, the crawl, index and rank pipeline that everything else builds on.