Facebook was founded in 2004 by Mark Zuckerberg and other Harvard students. It originally started as a social networking site for Harvard students but later expanded to other universities and then publicly in 2006. Key events included expanding internationally in 2009, reaching 500 million users in 2010, going public and reaching 1 billion users in 2012. Facebook now has over 1.44 billion monthly active users as of 2015, with the majority being mobile users. The site generates revenue primarily from advertising on the site and mobile apps. It has changed how people connect and share information online.