Answer engine
Also known as: AI search, generative search, LLM search
A system that answers a question directly by retrieving and summarising source pages, rather than returning a list of links to them.
ChatGPT search, Perplexity, Claude with web access, Google AI Overviews and Bing Copilot are all answer engines. They share a working method: retrieve a set of candidate documents, extract passages from them, and compose an answer that cites some subset.
The consequence for a website is that being retrievable and being quotable are now two different problems. A page can be perfectly indexed and still contribute nothing to an answer because nothing in it stands alone as a passage.
Answer engines mostly read the raw HTML response rather than a browser-rendered page. That single implementation detail is why a site can be visible in classic search and invisible in AI answers at the same time, and it is the gap the AI Discoverability reading exists to measure.