The Open Graph protocol enables any web page to become a rich object in a social graph. It means that if you want to control how your page looks when shared on Facebook, you’d better use the Open Graph meta tags in the part of a page.
Now, other social media sites are also taking advantage of social meta tags. All of the other major platforms, Twitter, LinkedIn, and Google+, recognize Open Graph tags.
The minimal set of Open Graph tags include:
og:title – The title of your object as it should appear within the graph, e.g., “The Rock”.
og:type – The type of your object, e.g., “video.movie”. Depending on the type you specify, other properties may also be required.
og:image – An image URL which should represent your object within the graph.
og:url – The canonical URL of your object that will be used as its permanent ID in the graph, e.g., “http://www.imdb.com/title/tt0117500/”.
You can find other types of Open Graph tags here.
Note: You can use the Facebook Debugger tool to check your Open Graph markup implementation.