A social contract is an implicit agreement among people, persons or agents that results in the organization of complex society, the individual surrenders liberty in return for protection, common resources and public goods. The notion of the social contract is that individuals unite into a society by a process of mutual consent, agreeing to abide by certain rules and to accept duties to protect one another from violence and fraud. Historically, "social contract" is a term used by Thomas Hobbes, John Locke, and Jean Jacques Rousseau to describe the appropriate relationship between individuals and their governments.
In a civilization or complex society, citizens gain civil rights in return for accepting the obligation to respect the common rules and laws. If too many members of a society break the social contract, i.e. if too many want to benefit from the public goods but nobody wants to contribute, it can lead to the "tragedy of the commons".