Educação Superior::Ciências Sociais Aplicadas::EconomiaPresents a class about imperfect information on Economics. In games, the person has consider that exist both simultaneous and sequential components, combining ideas from before and after the midterm. Rrepresent what a player does not know within a game using an information set: a collection of nodes among which the player cannot distinguish. This allows define games of imperfect information; and also lets us formally define subgames. Then extend our definition of a strategy to imperfect information games, and use this to construct the normal form (the payoff matrix) of such games. A key idea here is that it is information, not time per se, that matters. We show that not all Nash equilibria of such games are equally plausible: some are inconsistent with backward induction; some involve non-Nash behavior in some (unreached) subgames