Facebook was created by Mark Zuckerberg and his Harvard roommates originally for Harvard students and then expanded to all colleges before becoming open to anyone. It is now the largest social network and remains privately owned. While it allows users to connect with friends and find others they may have lost touch with, it can also be addictive and distract from real social interactions. Businesses can market on Facebook through ads or special pages but users should be cautious of privacy and security issues as employers may check profiles and content can be shared with third parties.