a.k.a. user-generated content, user-created content, social media, live Web, Web 2.0, pervasive awareness
On a broad level, it is an online community of people who are socializing with each other via a particular Web site. On an individual level, it is the practice of growing the number of one's business and/or social contacts by networking with individuals. Most of the social networks on the Web are public, allowing anyone to join. It is based on the idea of "six degrees of separation" (the concept that any two people on the planet could meet through a chain of no more than five people), social networking is a popular way to connect socially or professionally with other people!
Social networking websites offer their users an online community to share and explore common interests and activities. They typically provide a variety of ways for users to interact: through chat, messaging, email, video, voice chat, file-sharing, blogging, forums, discussion groups, and applications.
According to Danah Boyd, leading authority on social networking at U.C. Berkeley, the true definition of a "social network site" is that it contains profiles, semi-persistent public commentary on the profile, and a traversable publicly articulated social network displayed in relation to the profile. A "profile" includes a handle, information about that person, a photograph, and information about last login. Profiles have unique URLs that can be visited directly. "Semi-persistent public comments" means participants can leave comments (or testimonials, guestbook messages, etc.) on others' profiles for everyone to see. These comments may disappear over some period of time or upon removal and are reverse-chronological in display. Users of social networks value these features because comments and profiles are viewed as individuals' self-expression and because it shows what others say about the individual. "Traversable publicly articulated social network" means participants have the ability to list other profiles as "friends" or "contacts." The articulated social network is displayed on an individual's profile for all users to view. Each node contains a link to other profiles so that individuals can traverse the network through friends of friends.
Here's a list of social networking sites, see for yourself what it's all about:
In 2005, MySpace grew 400% with 28 million people online (most of them under 30). In the same year there were 19 million registrants at Friendster, most college students logging on at Facebook, and some 21 million individual blogs. Within 18 months, Flickr had one million users.
Social networking is also referred to by online marketers and researchers as "pervasive awareness" because they can "watch what people are saying and doing."