Facebook Connect allows users to log into external websites using their Facebook credentials. This allows the external site to access the user's social graph and profile data from Facebook and share content back to Facebook. The technology uses JavaScript and FBML tags to integrate Facebook features into a website. It allows functions like displaying Facebook profile info, publishing to Facebook, and recreating a user's social network on the external site. However, it only provides limited access to user data and has some disadvantages related to its reliance on JavaScript.