A-level Mathematics/OCR/D2/Game Theory
A zero sum game involves a series of players (usually two) where the total winnings is always zero. This means that at least one of them have to win, and similarly at least one must lose. A simple examples is a bet between two players A and B - the loser has to pay some money to the winner and hence the sum of the money won/lost by A and that of B is always zero.