Facebook recently added a “Send” button into it’s arsenal of social plugins that you see on pretty much every website and blog these days. Other famous social plugins from Facebook are the Like button, Comment box, Activity feed and Recommendations plugins, Facepile, Facebook login, Live stream and a few more. You can look at all the social plugins that Facebook has here: http://developers.facebook.com/docs/plugins/
The new plugin, the send button (access here) is another way to invite friends and share. Facebook has made it easy to use (like the other plugins), all you have to do is give the link that you want to send, and embed that link wherever you want. Then when a user clicks, “Send” a Send Box appears and the message can be sent to your friends or to an email. You can also include a personal message along with the link. The send button can also be combined with the like button.
HyperArts does a great job of explaining the Send Button in it’s most recent article. You can read more here