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"). The maximum size of social networks tends to be around 150 people and the average size around 124 (Hill and Dunbar, 2002).

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.