Extensive-Form Game

An extensive-form game represents a game as a tree of sequential decisions. Each nonterminal node specifies the player who moves, its outgoing edges specify the available actions, information sets identify decision nodes that a player cannot distinguish, and terminal nodes carry payoffs. A pure strategy specifies an action at every information set of a player, including information sets that may not be reached. Extensive form therefore records the timing and information structure that are absent from a normal-form game.