Facebook Connect is a single sign-on application that allows users to interact on other websites through their Facebook account. Launched in December 2008, Facebook Connect works with over 15,000 “partner” sites to make it easier for users to access the site.
When a user decides to access a third party site through Facebook Connect, they allow them to retrieve the information they have provided to Facebook, including full name, photos, wall posts, friend information, etc. This not only allows the user to skip the basic registration steps required by most sites, but also allows the site to update the Facebook wall and user news feed with their activities. By gaining access to the user’s friends list, the site can show the user which of their friends also accessed the site through Facebook Connect.
See More Information:
The Facebook Help Center answered frequently asked questions about Facebook Connect.
Facebook provides a guide on how to use Facebook Connect to customize a site and expand visitors.