Facebook is a social networking website launched in February 2004 and operated and privately owned by Facebook, Inc. Facebook was founded by Harvard student Mark Zuckerberg with his college roommates and fellow computer science students Eduardo Saverin, Dustin Moskovitz and Chris Hughes. Facebook headquarters relocated to Palo Alto, California in June 2004.

Users can add people as friends and send them messages, and update their personal profiles to notify friends about themselves. Additionally, users can join networks organized by workplace, school, or college. The website's name stems from the colloquial name of books given to students at the start of the academic year by university administrations in the U.S. with the intention of helping students to get to know each other better. Anyone age 13 or older can become a Facebook user.

The website's membership was initially limited by the founders to Harvard students, but was expanded to other colleges in the Boston area, the Ivy League and Stanford University. It later expanded further to include any university student, then high school students and, finally, to anyone aged 13 and over. The website currently has more than 500 million active users worldwide and, in 2010, annual revenue was predicted to top $1.1 billion.

Source: Facebook, Wikipedia