Some social network services are based on the premise that people have a set of "friends" or "contacts," and that when a user makes a connection to another user, they are both able to see each other's content, as well as the content of their mutual connections. Some allow users to organize their contacts into distinct groups, such as "friends", "family", and "coworkers".
Social network services let people interact with others by, for example, posting messages, images, and videos; sending messages and forming virtual communities to share interests. Social network services vary in format and the scope of capabilities they provide. Some social networks are based on real names, while others are based on pseudonyms or user-generated screen names.
Social networking services can facilitate online communities of practice that bring people together who share an interest in a subject and allow them to exchange information and ideas. There is a vast range of such communities based on diverse topics such as science, cooking, gaming, health, spirituality, and literature, among others. Additionally, some services can be based on location or region, which helps to connect local users.
