This document provides an overview of key concepts in microeconomics, including different market structures, oligopoly, game theory, and the prisoner's dilemma. It discusses how oligopoly involves a small number of interdependent firms competing in a market where demand and marginal revenue curves are not obvious and firms cannot find the profit-maximizing point using standard methods. It also introduces game theory and the Nash equilibrium concept developed by John Nash, using the prisoner's dilemma game as an example to illustrate how pursuing dominant strategies can result in non-cooperation.