Definition
Rich results are the enhanced SERP listings Google renders when valid schema.org markup is detected: FAQ accordions, recipe stars, product prices with availability, review aggregate ratings, breadcrumbs, sitelinks. The same schema also powers AI Overview eligibility. Google's Rich Results Test at search.google.com/test/rich-results validates markup before deploy.
An FAQ page with valid FAQPage schema can appear with an accordion-style snippet in Google's SERP and in AI Overviews. Without the schema, it appears as a plain link.
How to optimize
Pick one or two rich-result-eligible schema types per page. Validate before deploy. Track in Search Console's Enhancement reports.