The Social Graph is “the idea that if you mapped out all the connections between people and the things they care about, it would form a graph that connects everyone together.”
Source: Mark Zuckerberg
The social graph is a contextual sociogram that describes all the members, organizations, groups and other user-end components of a social network and the relation/connection between them. A social graph helps to illustrate and map the overall structure and interrelation of social network members.
The Social Graph is the representation of our relationships. In present day context, these graphs define our personal, family, or business communities on social networking websites.
Source: Jeremiah Owyang