Getting started with schema.org using Microdata
Most webmasters are familiar with HTML tags on their pages. Usually, HTML tags tell the browser how to display the information included in the tag. For example, <h1>Avatar</h1> tells the browser to display the text string "Avatar" in a heading 1 format. However, the HTML tag doesn't give any information about what that text string means—"Avatar" could refer to the hugely successful 3D movie, or it could refer to a type of profile picture—and this can make it more difficult for search engines to intelligently display relevant content to a user.
Schema.org provides a collection of shared vocabularies webmasters can use to mark up their pages in ways that can be understood by the major search engines: Google, Microsoft, Yandex and Yahoo!
You use the schema.org vocabulary along with the Microdata, RDFa, or JSON-LD formats to add information to your Web content. This guide will help get you up to speed with Microdata and schema.org so that you can start adding markup to your web pages.
Although this guide focuses on Microdata, most examples on the schema.org site show examples in RDFa and JSON-LD too. The basic ideas (types, properties etc.) introduced here are relevant beyond Microdata - take a look at the examples to see how the details compare.