AI engines don't answer your query — they answer the fan-out.
When someone asks ChatGPT, Perplexity, or Google AI Mode a question, the engine expands it into many sub-queries, retrieves results for each, and synthesizes one answer. If your content only targets the head term, you're invisible for the dozens of variations the engine actually retrieved against. Query fan-out is the single biggest mental-model shift from classic SEO to AI search.