A search engine ranks pages. An answer engine extracts claims and reassembles them, so the unit of competition has changed from the page to the passage. Content that buries its answer under four paragraphs of throat-clearing does not get quoted, whatever it ranks for.
What works is unglamorous. State the answer immediately, then justify it. Use the words people actually type as headings. Put numbers in tables rather than in prose. Answer the questions people ask rather than the ones that flatter the product.
The credibility mechanics matter more than in classic search: named sources, dates, and an author that resolves to something. A confident, unattributed claim is exactly what a careful system declines to repeat.
What is answer engine optimisation?
Structuring content so an AI assistant can extract and quote it accurately: the answer stated in the opening lines, real headings, numbers in tables, and sources that can be checked.
How is it different from SEO?
Classic SEO competes at the level of the page. Answer engines extract passages, so a page can rank well and still never be quoted if its answer is buried.