Facebook is the largest social networking site worldwide.
The site was co-founded in 2004 by Mark Zuckerberg while still a student at Harvard College in Cambridge, Mass. Membership was initially limited to Harvard students but the site eventually opened to other college and high school students. Membership was extended to anyone with a valid email address in 2006.
Some of Facebook's early investors included PayPal co-founder Peter Thiel and Microsoft. Napster founder Sean Parker was Facebook's founding president.
Facebook allows users to create profiles than can include photos, personal interests and contact information. Users can communicate over a variety of public and private posting features.
The site has also become a useful marketing tool for businesses and brands, including Entrepreneur Magazine.
Facebook went public in 2012 and raised more than $100 billion.
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