Structured Data
Data organized into a consistent, predictable format -- fields and types are known in advance, unlike free-form text.
Structured data follows a consistent, predictable format: defined fields, known data types, and a fixed (or versioned) layout. It's the opposite of unstructured data like a paragraph of prose or a scanned image. Structured data is what makes a dataset queryable, exportable, and machine-readable -- and it's also what schema.org markup and llm.txt files rely on to describe a page to search engines and AI systems.
Example
A JSON file of products with `sku`, `title`, and `price` fields is structured data. A blog post about those same products is not, until it's marked up with schema.org Product structured data.