Schema.org is a collaborative project between major search engines such as Google, Bing, Yahoo, and Yandex to create a standardized vocabulary of tags (or schema) that can be added to websites’ HTML code to provide more structured data to search engines.

Structured data refers to a standardized format for providing information about a page and its content, such as the title, author, description, image, and more. By using schema.org markup, webmasters can help search engines understand the content on their pages more effectively and provide richer, more informative search results for users.

In summary, Schema.org provides a standard set of tags for websites to use that helps search engines understand the content better and provide more informative search results for users.