Facebook is a social networking service for high school, college, university, corporate, non-profit, and geographic communities primarily in English-speaking countries. The site has some similarities to MySpace, but differs in account availability, user control of display content, real-world identity, and overall neatness of appearance. As of December 2005, it has the largest number of registered users among college-focused sites (at over six million US college student accounts created with an additional 20,000 new accounts being created daily). It is the number one site for photos, ahead of public sites such as flickr, with 1.5 million photos uploaded daily and is the seventh most trafficked site in the United States.

Anyone with access to a valid e-mail address from 2,000+ universities can register for and access the site. This includes university students, alumni, faculty, and staff, although the vast majority of Facebook’s users are students. Facebook is also available at 25,000+ American and Canadian high schools as well as 850+ corporations and non-profit organizations, such as Microsoft, Pepsi and Teach for America. The site is free to users and generates revenue from advertising including banner ads and sponsored groups (revenue is rumored to be over $1 million per week). Users create personal profiles, typically containing photos and lists of interests, exchange private or public messages, and join groups of friends. The viewing of detailed profile data is restricted to users from the same school or confirmed friends. The site boasts incredible usage statistics as, according to TechCrunch, "about 85% of students in supported colleges have a profile [on the site]. [Of those who are signed up,] 60% log in daily. About 85% log in at least once a week, and 93% log in at least once a month."

Facebook employs people in Palo Alto, California and in Boston, Massachusetts. The name of the site is based on the paper facebooks that many colleges give to incoming students, faculty, and staff depicting members of the campus community.