Schema Markup

A form of microdata that helps search engines understand the content on your website by providing structured data about your pages.

Examples

Structured Data: Structured data is a standardized format for providing information about a page and classifying the page content.
JSON-LD: JSON-LD (JSON for Linked Data) is a method of encoding Linked Data using JSON. It is a lightweight syntax to express structured data.
Microdata: Microdata is a WHATWG HTML specification used to nest metadata within existing content on web pages.
RDFa: RDFa (Resource Description Framework in Attributes) is a W3C Recommendation that adds a set of attribute-level extensions to HTML.

Reference: schema.org