1. Facebook is a social networking website launched in 2004 that allows users to create profiles, add friends, join groups, and share updates and messages. 2. Users can customize their profile by adding photos, interests, and other information and communicate privately or publicly with friends through messages or chat. 3. In addition to sharing updates on walls and with friends, Facebook has features for sending gifts, buying and selling items, commenting on friends' statuses, and creating events.