MIT's 14.12 Economic Applications of Game Theory continues with instructor Ian Ball formalizing how games are represented for analysis. He works through extensive-form games, which track the sequence of moves and information available to each player at each decision point, and strategic-form games, which reduce a game to the set of strategies and payoffs available to each player. Ball defines what a strategy actually means in this context, distinguishing it from a simple action, and shows how any extensive-form game can be translated into its strategic-form equivalent. The seventy-three minute session builds the notation and vocabulary, players, information sets, payoffs, that the rest of the course will use to analyze strategic interaction among multiple decision-makers. It is a blackboard lecture aimed at students who have already been introduced to the basic idea of a game in the first session.