A family of standard web feed formats used to publish frequently updated information like blog entries, news headlines, audio and video.
Open graph description entity tag
The Open Graph protocol enables any web page to become a rich object in a social graph, a open protocol supported by Facebook
Chrome for Android, since version 39 supports the "theme-color" meta tag to allow websites control the background color of the tab's UI header.
Sites who has this tag are verfied by google to use WebMaster tools