Probability and odds are related ways of describing a player's chances of a winning outcome. The probability of an event is the number of ways that an event can happen, set against the total number of possible events that could happen. Probability allows us to predict how often an event will occur, but does not allow us to predict when exactly an event will occur. Probability is useful in player decision-making. Understanding probability can help you understand what is the likely long-term bottom line of a particular game and if the game is worth the money spent to play. Odds can be an exact measure of win probability, but are subjective in many gambling games. When odds are referred to in games of pure chance, the percentage is a precise mathematical computation of win probability. When odds are referred to in games of skill, it is a subjective estimate of payout for each unit bet.