Facebook "Send" button as well as "Like" lets users to share a web page with their friends.
Unlike the "Like" button, "Send" button doesn't create a posting on the wall, but allows to directly send a link leading to web page to a Facebook friend looking them up by name or email. It's also possible to send links to Facebook groups.
On Getsocio, Facebook "Send" button will appear automatically, on every published deal after you set up Facebook Application and enable "Facebook sharing" option under Facebook tab at The Settings page in Admin section.