Facebook Chat is an instant messaging service offered by social network Facebook. It does not use an application, but is web-based and appears at the bottom of every Facebook page, informing users which of their friends are online and available to chat. Facebook Chat was officially released on April 6, 2008, but was not available to all users at the time of launch. Facebook announced that they would roll out the product slowly, and users can expect the chat bar to appear on their profiles "very soon." Fast Facts:

1. Was launched on April 6, 2008
2. One-to-one chat only
3. No 3rd party integration at launch

Although the primary use for Facebook Chat is to chat with friends who are on the site, it also serves to instantly deliver notifications of any site activity. When a friend posts a comment on a user's wall, for example, instead of having to reload the page to see the notification of the posting, an icon appears in the Facebook Chat bar at the bottom of the screen, indicating that the user has an unread notification or several unread notifications. It is a small feature, but it eliminates the need to refresh the page. This ties in well to the chat application's primary fuction, as users need only log into Facebook to stay on top of site activity relating to them.