Structured data is a standardized way to describe webpage content so software can identify entities, properties, and relationships without relying only on free-form text. It can clarify that a page contains an article, product, organization, event, person, offer, or another supported entity when the markup accurately reflects the page.
The dominant vocabulary is Schema.org. It defines entity types such as Article, Product, LocalBusiness, and many others, together with properties that describe those entities. The vocabulary is broader than Google's search-feature support, so a valid Schema.org type does not automatically create a Google rich result.
The common syntax choices are:
- JSON-LD - Structured data expressed in a script block. It is usually easier to manage separately from visible HTML and is the format Google commonly recommends for supported use cases.
- Microdata - Structured data attributes embedded directly in HTML elements. It can work correctly but may be more tightly coupled to template markup.
- RDFa - Attribute-based structured data that can also express semantic relationships within HTML.
What structured data does not do is guarantee a ranking improvement or a specific search appearance. A supported implementation can make content eligible for certain Google search features, but display remains Google's decision and depends on current documentation, page quality, content accuracy, and other search-system considerations.
Structured data can also provide machine-readable entity information beyond a visible rich result. That does not justify claims that it is a special requirement for Google AI Overviews or other Google AI features unless Google explicitly documents such a requirement.