Structured data is standardized code added to a page that labels the meaning of its content, telling machines that a block of text is a product, a price, an author, an FAQ, and so on. The most common vocabulary is Schema.org, usually implemented in the JSON-LD format.
For brands, structured data is best understood as hygiene rather than a primary lever. It helps machines parse your content cleanly and supports rich results in traditional search, but controlled studies have found its direct causal effect on AI citations is small, and most AI assistants do not read schema directly. Ship the basics on every page, but do not expect markup alone to move AI visibility.