According to boyd, d. m., & Ellison, N. B. (2007) social network sites are web-based services that facilitate users in creating a public or semi-public profile within a their network system. They display a list of other users sharing some kind of connection, and allow users to view and negotiate their list links and those made by others within the network. These connections can vary in their types types and titles.
The various network sites allow users to meet others with like interests, and they also make it possible for all their networked contacts to see each others contacts. This makes it possible for connections to be made that would not otherwise be made, but mostly it creates a platform for sharing and communicating (boyd, d. m., & Ellison, N. B. 2007.)
Social network sites also vary greatly in their features and types of users. They can also facilitate professional networking, and make this a feature of their structure. An example of this would be LinkedIn. Others target specific interest groups, cultural or language groups. Some provide photo-sharing or video-sharing capabilities and others have built-in blogging and instant messaging technology. (boyd, d. m., & Ellison, N. B. 2007.)
Often users can access their network using mobile devices. Social Network sites have become a global phenomenon. Love them or hate them, they are evolving and proliferating.
boyd, d. m., & Ellison, N. B. (2007). Social network sites: Definition, history, and scholarship. Journal of Computer-Mediated Communication, 13(1), article 11.