Facebook was created by Mark Zuckerberg and others at Harvard in 2004. It was originally only for Harvard students but expanded to other colleges and then publicly. Facebook now has over 1 billion daily active users and allows people to connect with friends and family, share photos and updates, see others' profiles and newsfeeds, and use it for events and businesses. While it helps people stay in touch, there are also risks like bullying, privacy issues, and overuse.