Social plugins enable you to provide engaging social experiences to your users with just a line of HTML. Because they are hosted by Facebook, the plugins are personalized for all users who are logged into Facebook — even if the users haven’t yet signed up for your site.

The new Graph API attempts to drastically simplify the way developers read and write data to Facebook. It presents a simple, consistent view of the Facebook social graph, uniformly representing objects in the graph (e.g., people, photos, events, and fan pages) and the connections between them (e.g., friend relationships, shared content, and photo tags).