The theory of the core reveals a sense in which the outcome of trading under a price system is stable in an economy that contains many agents. Game theory uses mathematics to express its ideas formally. However, most game theoretical ideas are not inherently mathematical, though a mathematical formulation makes it easy to define concepts precisely, to verify the consistency of ideas, and to explore the implications of assumptions. A game is a description of strategic interaction that includes the constraints on the actions that the players can take and the players' interests, but does not specify the actions that the players do take. A solution is a systematic description of the outcomes that may emerge in a family of games.
Game theory suggests reasonable solutions for classes of games and examines their properties.
In all game theoretic models the basic entity is a player . A player may be interpreted as an individual or as a group of individuals making a decision. Two basic types of noncooperative model are that of a strategic game and that of an extensive game . Another distinction between types of games concerns the information the players are assumed to possess. In some models the participants are fully informed about each others' moves, while in others they may be imperfectly informed.