What Is SEO? – Definition and How It Works
Learn what search engine optimisation covers, its three pillars, what has changed with AI answers, and which practices remain durable.
Search engine optimisation is making a site more likely to be found through search. It divides into technical work, content work, and authority work, and the durable parts have changed less than the discourse suggests.
1. The Three Pillars
| Pillar | Concerns |
|---|---|
| Technical | Crawlability, rendering, speed, structure, indexation |
| Content | Intent match, depth, clarity, and structure |
| Authority | References from elsewhere, and consistency over time |
All three are necessary. A fast, crawlable site with content nobody needs does not rank; excellent content on an uncrawlable site cannot be found.
2. Technical Work Is a Precondition
If a page cannot be fetched, rendered, and understood, nothing else matters. That means server-rendered or hydrated content, honest canonicals, clean internal linking, a valid sitemap, correct status codes, and fast responses.
None of this earns rankings by itself. All of it is required before content and authority can.
3. Content Work Is Intent Work
The single most common failure is producing something excellent for a query that wanted something else. A comparison query returns comparisons; a product page will not displace them.
Reading the results page to determine intent, then matching format before competing on depth, is the whole of it.
4. Authority Accumulates
References from other sites remain a substantial signal, and they are earned rather than acquired — by publishing things worth citing, over time.
Practices that attempt to shortcut this are the ones most reliably devalued, which is why the durable strategy is unglamorous.
5. What AI Answers Changed
Generated summaries and answer engines shifted the target for informational queries. Where a snippet or overview satisfies a question, the click may not follow.
What that changed in practice:
- Passage-level structure matters more — the unit competing for citation is a section, not a page.
- Specificity matters more — checkable claims survive summarisation; adjectives do not.
- Measurement changed — presence in generated answers is a sampled rate, not a position.
- Accuracy of description became a metric — how an engine characterises you is now worth tracking.
6. What Did Not Change
Crawlability, speed, intent match, clear structure, and earned authority all still apply — and all of them help with generated answers as much as with ranked links.
The overlap is high enough that treating the two as separate disciplines mostly duplicates work.
7. What Reliably Does Not Work
- Keyword density and exact-match repetition.
- Thin pages produced at volume to cover terms.
- Structured data describing content the page does not contain.
- Blocking AI crawlers as a strategy, which removes your words from the pool that describes you.
- Anything designed to look like a signal rather than to be one.
8. Summary
SEO combines technical accessibility, content that matches intent, and authority earned over time — with technical work as a precondition rather than an advantage.
Generated answers raised the value of passage-level structure and specific claims, and changed measurement from positions to sampled rates. The underlying practices are the same ones, applied with the section rather than the page as the unit.