A social network is a social structure made of nodes which are generally individuals or organizations. It indicates the ways in which they are connected through various social familiarities ranging from casual acquaintance to close familial bonds. The term was first coined in 1954 by J. A. Barnes (in: Class and Committees in a Norwegian Island Parish, "Human Relations").
Social network analysis (also called network theory) has emerged as a key technique in modern sociology, anthropology, social psychology, information science and organizational studies, as well as a popular topic of speculation and study. Research in a number of academic fields have demonstrated that social networks operate on many levels, from families up to the level of nations, and play a critical role in determining the way problems are solved, organizations are run, and the degree to which individuals succeed in achieving their goals.
Social networking also refers to a category of Internet applications to help connect friends, business partners, or other individuals together using a variety of tools. These applications, known as online social networks are becoming increasingly popular.
Social network theory views social relationships in terms of nodes and ties. Nodes are the individual actors within the networks, and ties are the relationships between the actors. There can be many kinds of ties between the nodes. In its most simple form, a social network is a map of all of the relevant ties between the nodes being studied. The network can also be used to determine the social capital of individual actors. These concepts are often displayed in a social network diagram, where nodes are the points and ties are the lines.
The shape of the social network helps determine a network's usefulness to its individuals. Smaller, tighter networks can be less useful to their members than networks with lots of loose connections to individuals outside the main network. More "open" networks, with many weak ties and social connections, are more likely to introduce new ideas and opportunities to their members than closed networks with many redundant ties. In other words, a group of friends who only do things with each other already share the same knowledge and opportunities. A group of individuals with connections to other social worlds is likely to have access to a wider range of information. It is better for individual success to have connections to a variety of networks rather than many connections within a single network. Similarly, individuals can exercise influence or act as brokers within their social networks by bridging two networks that are not directly linked (called filling social holes).
The power of social network theory stems from its difference from traditional sociological studies, which assume that it is the attributes of individual actors -- whether they are friendly or unfriendly, smart or dumb, etc. -- that matter. Social network theory produces an alternate view, where the attributes of individuals are less important than their relationships and ties with other actors within the network. This approach has turned out to be useful for explaining many real-world phenomena, but leaves less room for individual agency, the ability for individuals to influence their success, so much of it rests within the structure of their network.
Social networks have also been used to examine how companies interact with each other, characterizing the many informal connections that link executives together, as well as associations and connections between individual employees at different companies. These networks provide ways for companies to gather information, deter competition, and even collude in setting prices or policies.
Social network theory is an extremely active field within academia. The International Network for Social Network Analysis is an academic association of social network analysts. Many social network tools for scholarly work are available online (like "UCINet" or the "network" package in "R") and are relatively easy to use to present graphical images of networks.
Diffusion of innovations theory explores social networks and their role in influencing the spread of new ideas and practices. Change agents and opinion leaders often play major roles in spurring the adoption of innovations, although factors inherent to the innovations also play a role.
The first social networking website was Classmates.com, which began in 1995. Other sites followed, including SixDegrees.com, which began in 1997. It was not until 2001 that websites using the Circle of Friends online social networks started appearing. This form of social networking, widely used in virtual communities, became particularly popular in 2003 and flourished with the advent of a website called Friendster. There are over 200 social networking sites. The popularity of these sites rapidly grew, and by 2005 MySpace was getting more page views than Google.  Google has a social network called orkut, launched in 2004. Social networking began to be seen as a component of internet strategy at around the same time: in March 2005 Yahoo launched Yahoo 360, their entry into the field, and in July 2005 News Corporation bought MySpace. .
In these communities, an initial set of founders sends out messages inviting members of their own personal networks to join the site. New members repeat the process, growing the total number of members and links in the network. Sites then offer features such as automatic address book updates, viewable profiles, the ability to form new links through "introduction services," and other forms of online social connections. Social networks can also be organized around business connections, as for example in the case of Shortcut or LinkedIn.
Blended networking is an approach to social networking that combines both offline elements (face-to-face events) and online elements. MySpace, for example, builds on independent music and party scenes, and Facebook mirrors a college community. The newest social networks on the Internet are becoming more focused on niches such as art, tennis, football (soccer), golf, cars, dog owners, and even cosmetic surgery.
Most of the social networks on the internet are public, allowing anyone to join. Organizations, such as large companies, also have access to private social networking applications, known as Enterprise Relationship Management. They install these applications on their own servers and enable employees to share their networks of contacts and relationships to outside people and companies.
In June of 2006 Friendster won a U.S. patent on the popular system and practice of social networking.
- Year in Review 2006 - Social Networking from C|Net