See what your Facebook friends have liked, shared, or commented on across the Web. This includes all variations of Like, Share and Follow Buttons, Embedded Posts, Comments, Activity Feed, Recommendations Feed, Recommendations Bar, Like Box and Facepile.
Open graph description entity tag
Any offered product or service. For example: a pair of shoes; a concert ticket; the rental of a car; a haircut; or an episode of a TV show streamed online.
Sites who has this tag are verfied by google to use WebMaster tools
A canonical link element is an HTML element that helps webmasters prevent duplicate content issues by specifying the "canonical", or "preferred".
By adding rel="home" to a hyperlink, a page indicates that the destination of that hyperlink is the homepage of the site in which the current page appears.