A social network service focuses on building online communities of people who share interests and activities, or who are interested in exploring the interests and activities of others. Most social network services are web based and provide a variety of ways for users to interact, such as e-mail and instant messaging services.
Social networking has created powerful new ways to communicate and share information. Social networking websites are being used regularly by millions of people, and it now seems that social networking will be an enduring part of everyday life. The main types of social networking services are those which contain directories of some categories (such as former classmates), means to connect with friends (usually with self-description pages), and recommender systems linked to trust. Popular methods now combine many of these, with MySpace and Facebook being the most widely used in North America; Bebo, MySpace, Skyrock Blog, StudiVZ, Youmeo, Facebook and Hi5 in parts of Europe; Orkut and Hi5 in South America and Central America; and Friendster, Orkut, and Cyworld in Asia and the Pacific Islands. CouchSurfing is a new type of social network called hospitality exchange networks.

History of social networking services
The notion that individual computers linked electronically could form the basis of computer mediated social interaction and networking was suggested early on . There were many early efforts to support social networks via computer-mediated communication, including Usenet, ARPANET, LISTSERV, bulletin board services (BBS), and EIES: Murray Turoff's server-based Electronic Information Exchange Service (Turoff and Hiltz, 1978, 1993). The Information Routing Group developed a schema about how the proto-Internet might support this.
Early social networking websites included Classmates.com (1995), focusing on ties with former school mates, and SixDegrees.com (1997), focusing on indirect ties. User profiles could be created, messages sent to users held on a “friends list” and other members could be sought out who had similar interests to yours in their profiles Whilst these features had existed in some form before SixDegrees.com came about, this would be the first time these functions were available in one package. Despite these new developments (that would later catch on and become immensely popular), the website simply wasn’t profitable and eventually shut down . It was even described by the website’s owner as “simply ahead of its time.” Two different models of social networking that came about in 1999 were trust-based, developed by Epinions.com, and friendship-based, such as those developed by Jonathan Bishop and used on some regional UK sites between 1999 and 2001. Innovations included not only showing who is "friends" with whom, but giving users more control over content and connectivity. By 2005, one social networking service MySpace, was reportedly getting more page views than Google, with Facebook, a competitor, rapidly growing in size. In 2007, Facebook began allowing externally-developed add-on applications, and some applications enabled the graphing of a user's own social network - thus linking social networks and social networking.
Social networking began to flourish as a component of business internet strategy at around March 2005 when Yahoo launched Yahoo! 360°. In July 2005 News Corporation bought MySpace, followed by ITV(UK) buying Friends Reunited in December 2005. Various social networking sites have sprung up catering to different languages and countries. It is estimated that combined there are now over 200 social networking sites using these existing and emerging social networking models, without counting the niche social networks (also referred to as vertical social networks) made possible by services such as Ning and KickApps.

Social networks for social good
Several websites are beginning to tap into the power of the social networking model for social good. Such models may be highly successful for connecting otherwise fragmented industries and small organizations without the resources to reach a broader audience with interested and passionate users. Users benefit by interacting with a like minded community and finding a channel for their energy and giving. [28] Examples include SixDegrees.org and Network for Good. The charity badge is often used within the above context.