Facebook is a social utility that enables people to understand the world around them. Facebook develops technologies that facilitate the spread of relevant information through social networks, allowing people to share information online the same way they do in the real world. Facebook is made up of many networks - individual schools, companies or regions - each of which are independent and closed off to non-affiliated users. To join Facebook, people can authenticate into a school or work network, or they can join a regional network. They can then create profiles to connect with friends, share interests, join groups, send messages, write notes and post photos. Facebook gives people control over what information they share and with whom they share it. Using Facebook's privacy settings, people can limit the information visible to someone or block that person from seeing them completely. The ability to control their information means people can stay current with their friends and the people around them in a trusted environment.