Glossary

Generative engine optimization (GEO)

The practice of structuring content, entities and third-party presence so that AI answer engines cite a brand when generating a response. Where classic SEO competes for a ranked position among ten links, GEO competes for a mention inside a single synthesised answer that names only a handful of sources.

Also called AEO or AI search optimization. None has settled as standard, and the practices described under each overlap almost entirely.

Answer engine optimization (AEO)

A synonym for generative engine optimization. Some practitioners draw a distinction — AEO for direct-answer features, GEO for generated prose — but the distinction is not observed consistently and no engine documents it. Treat the terms as interchangeable and ask what someone means before agreeing to buy it.

The five gates

A diagnostic frame: every search or AI-answer failure occurs at one of five stages. Crawl — can a bot fetch the URL? Index — did the engine keep it? Retrieve — was it pulled for this query? Cite — was it named in the answer? Influence — did it shape what the answer said?

Classic SEO lives at gates one and two. AI-answer visibility lives at three, four and five. How each one fails, in detail →

Query fan-out

Google's term for the way a generative search feature rewrites a single user question into multiple concurrent sub-queries, each retrieving separately. The practical consequence is that you no longer compete for one keyword but across the set of sub-questions your buyer's question decomposes into — which changes what a page has to contain.

Retrieval crawler vs training crawler

Two different jobs, frequently conflated in the same robots.txt. A retrieval crawler fetches pages to answer a live question and to attribute sources — blocking it removes any possibility of being cited today. A training crawler gathers data to train future models — blocking it affects model weights later and is a slower, more arguable harm.

A third category is neither: tokens such as Google-Extended and Applebot-Extended are directives, not crawlers. No agent fetches under those names; Googlebot and Applebot do the fetching, and the tokens govern what the content is subsequently used for.

robots.txt vs noindex

If you disallow a URL in robots.txt, the crawler never fetches it, therefore never sees the noindex — and the URL can still appear in results. To remove something from an index you must allow it to be crawled.

Render queue

Google renders JavaScript, but not immediately. Pages that return 200 enter a deferred rendering queue and may wait there considerably longer than the few seconds people assume. Content that only exists after hydration is therefore delayed for Google and frequently invisible to AI retrieval crawlers, most of which do not render at all.

Soft 404

A page that returns HTTP 200 while actually being a "not found" state — most often a host serving the homepage for every unmatched URL. It tells a crawler that every mistyped path is real content, which is how sites accumulate thousands of duplicate pages nobody wrote. Fixed by returning a genuine 404 status.

llms.txt

Ahrefs found 97% of llms.txt files received zero requests in a month across 137,000 domains. It costs about an hour to publish and carries no downside, so publish one if you like — but nobody should be charging you for it as a mechanism.

Structured data

Machine-readable markup, usually schema.org JSON-LD, describing what a page is about. It is not a ranking factor. It creates eligibility for rich results, which is a different and narrower claim. Google states that no special structured data is needed to appear in its AI features.

FAQ rich results were retired entirely in 2026 — they stopped appearing in May, documentation was removed in June, and Search Console API support went in August. An agency still selling FAQ schema for star ratings is working from a stale map.

Core Web Vitals

Three field-measured metrics: LCP (largest contentful paint, good ≤ 2.5s), INP (interaction to next paint, good ≤ 200ms) and CLS (cumulative layout shift, good ≤ 0.1). Measured at the 75th percentile over a 28-day rolling window of real Chrome traffic.

Lab tools measure one device on one network; only field data is what Google uses. A green Lighthouse score alongside a failing Search Console report is not a contradiction. Treat these as a tie-breaker and a conversion lever, not a primary ranking strategy.

Crawl budget

The volume of crawling an engine will spend on a site. Almost no site has a crawl budget problem — Google's rough thresholds are a million-plus pages changing weekly, or ten thousand-plus daily. Below that it is a distraction, and an agency raising it on a small site is a tell.

Citation vs mention

A mention is being named in an answer. A citation is being named as a linked source for it. The two come apart constantly: engines routinely name a brand while citing a directory or a video that describes it. Being mentioned without being cited means someone else's page is deciding how you are characterised.

Zero-click search

A search that ends without the user clicking through to any result. Measured rates vary by panel and method, and the figures quoted in this industry rarely carry their denominator. Ask for the sample size, the country and the window before accepting any of them, including ours.