Definition
Query fan-out is the way an answer engine expands one question into several smaller searches. “The best vacuum for a home with pets” can become separate searches about suction, filters, noise, price range and reviews.
Your page competes in each of those searches separately. A product page that covers only the headline question may be retrieved for none of the sub-queries, while a page that also states noise levels and filter costs is retrieved for several.
Why it matters
It explains why specific, complete pages win: the engine is asking several questions at once, and the page that answers more of them is cited more often.
How it works
Write pages around the sub-questions a buyer actually has, not around one keyword. Comparison tables, specification lists and FAQs give the engine something to retrieve for each part of the question.
