Answer Engine Optimization (AEO) is the discipline of shaping your site, your sources, and your evidence so that when someone asks an AI assistant for a recommendation in your category, the assistant names your product. It is the AI-era counterpart to SEO. Where SEO moves your URL up a list of ten blue links, AEO moves your brand into a one-sentence answer.
Why AEO is different from SEO
A search engine returns a list. An answer engine returns a sentence. Buyers do not click ten links any more for a comparison question. They paste it into ChatGPT or Perplexity and read the answer. If your product is not in that sentence, you do not exist for that purchase. AEO measures whether you are in the sentence, and what to change so you are.
What AEO actually measures
The core metric is mention rate: across many runs of the same buyer question, what percentage of answers name your brand. AI answers are stochastic, so a single prompt is not a measurement. You need to sample the same question dozens of times across each model to get a stable signal. AEO programmes also track competitor mention rate (who is named when you are not) and citation depth (which pages and sources the model leans on when it answers).
How to start
Pick five to ten buyer questions you wish AI answered with your name. Run each one 25-50 times across ChatGPT, Claude, Gemini, and Perplexity. Record who is named. Look at the citations the models surface. The gap between your mention rate and your top competitor's mention rate, plus the sources behind the gap, is your AEO roadmap.