The founders initially limited the website's membership to Harvard students and subsequently Columbia, Stanford and Yale students. Membership was eventually expanded to the remaining Ivy League schools, MIT, and higher education institutions in the Boston area. Facebook gradually added support for students at various other universities, and eventually to high school students.
Since 2006, anyone who claims to be at least 13 years old has been allowed to become a registered user of Facebook, though variations exist in this requirement, depending on local laws. The name comes from the face book directories often given to American university students. Facebook held its initial public offering (IPO) in February 2012, valuing the company at $104 billion, the largest valuation to date for a newly listed public company. It began selling stock to the public three months later. Facebook makes most of its revenue from advertisements that appear onscreen.
Facebook can be accessed from a large range of devices with Internet connectivity, such as desktop computers, laptops and tablet computers, and smartphones. After registering, users can create a customized profile indicating their name, occupation, schools attended and so on.
Users can add other users as "friends", exchange messages, post status updates, share photos, videos and links, use various software applications ("apps"), and receive notifications of other users' activity. Additionally, users may join common-interest user groups organized by workplace, school, hobbies or other topics, and categorize their friends into lists such as "People From Work" or "Close Friends". Additionally, users can report or block unpleasant people.
According to Wikipedia