Facebook is a free social networking service that generates income through advertising. It has over 845 million monthly active users globally. Key products include user profiles, photos, groups, and the newer Timeline feature. While the core service is free for users, Facebook makes money from advertisers who pay for ads and sponsored stories on the platform. Facebook can be accessed online through computers or mobile apps, and the company is headquartered in California with over 3,000 employees currently. Promotion of the platform involves businesses creating Facebook pages to engage with customers through regular posts, responses, and ultimately advertising placements. The company was founded by Mark Zuckerberg and several fellow Harvard students.