Facebook's Like button is the quickest way for people to share content with their friends. A single click on the Like button will 'like' pieces of content on the web and share them on Facebook. You can also display a Share button next to the Like button to let people add a personal message and customize who they share with.
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.
A scheme.org entity that represents an organization such as a school, NGO, corporation, club, etc.
A scheme.org entity that represents a person (alive, dead, undead, or fictional).
A scheme.org entity that represents an article, such as a news article or piece of investigative report. Newspapers and magazines have articles of many different types and this is intended to cover them all.
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".