In Briefcase, players build their own business empires by acquiring and activating various companies. Each company, once activated, provides the player with some benefits (which are called decisions cards) and a special ability for the rest of the game.
Players start with identical decks of decision cards. Each time one player activates a company, he/she adds to his deck more decision cards. Decision cards give the players various possible actions (like buy/activate/hire/obstacles). The most important is the "buy" action, with which players can either buy a building or a resource from the market.