What is Schema markup?

Schema markup is structured data embedded in a web page — typically as JSON-LD in a <script> tag — that tells search engines and AI assistants what the page is about in machine-readable form. The vocabulary is defined at schema.org, jointly maintained by Google, Microsoft, Yahoo, and Yandex. The schema types most relevant to AI UGC and e-commerce marketing are Product, Review, Article, FAQPage, HowTo, BreadcrumbList, Organization, and VideoObject. Schema is the single highest-leverage on-page intervention for AI search visibility: LLM citation pipelines parse JSON-LD as their first-pass source of entity, price, rating, and authorship signals because it is unambiguous and trivially indexable. The same Product, FAQPage, and Article schema that earns rich snippets in Google search materially increases the page's probability of being cited inside AI Overviews, Perplexity answers, and ChatGPT browsing results. Schema is not a ranking factor per se in classical SEO — but it is functionally a ranking factor in AI search.