What is Schema.org?
This site provides a collection of schemas, i.e., html tags, that
webmasters can use to markup their pages in ways recognized by
major search providers. Search engines including Bing, Google,
Yahoo! and Yandex rely on this markup to improve the display of
search results, making it easier for people to find the right web
pages.
Many sites are generated from structured data, which is often
stored in databases. When this data is formatted into HTML, it
becomes very difficult to recover the original structured
data. Many applications, especially search engines, can benefit
greatly from direct access to this structured data. On-page markup
enables search engines to understand the information on web pages
and provide richer search results in order to make it easier for
users to find relevant information on the web. Markup can also
enable new tools and applications that make use of the structure.
A shared markup vocabulary makes it easier for webmasters to decide
on a markup schema and get the maximum benefit for their efforts.
So, in the spirit of sitemaps.org, search engines have come
together to provide a shared collection of schemas that webmasters
can use.