For twenty years, being found online meant earning a place on a page of ten links. The buyer did the reading, opened a few tabs and made up their own mind. That page still exists, but more and more of the reading now happens before anyone clicks. Search engines summarise, assistants compare and a buyer can get a shortlist in one reply.
That changes the question a business has to ask. It is no longer only "where do we rank?" but also "what do these systems say about us, and do they say it at all?" An answer engine can only recommend what it can find, read and confirm. If your pricing is hidden in a PDF, your services are described differently on every profile, or nobody outside your own site mentions you, the answer will be written without you.
Answer engine optimization is the discipline of fixing that. It starts with measuring how you appear today, then improves the content, structure and outside evidence that answers are built from. It sits on top of good SEO rather than replacing it, and it is judged by the same thing every marketing investment is judged by: more of the right people getting in touch.