Facebook is a social networking site launched in 2004 with over 1 billion active users. Users create personal profiles, add friends, and share messages and updates. Additionally, users can join groups and categorize friends. Facebook was founded by Mark Zuckerberg and others at Harvard. Initially for Harvard students, it expanded to other schools and is now open to anyone over 13. Facebook allows socialization, sharing of life updates, advertising, advocacy sharing, and gaming.