A win-win situation, also called a win-win game or non-zero-sum game in game theory, is a situation by which cooperation, compromise, or group participation leads to all participants benefiting. The term can be applied to many aspects of daily living, and it is contrasted to the zero-sum game or win-lose situation, where the dominant factor is that at least one person wins while another loses. These are also called zero-sum games and examples include most two-person board games. For instance a chess game is zero-sum. One winner, +1, is added to one loser, -1, resulting in a total of zero.
The win-win situation is different, since its total according to game theory could be two or more. In a two-person scenario, where both people could cooperate and thus benefit, this could be mathematically expressed and +1 plus +1 = 2. Instead of a situation creating a winner and a loser, both people win a roughly equivalent amount.
You can apply the term win-win situation to any small negotiations in life. A typical comparison might be compromise between a husband and wife on an issue of contention. Perhaps the couple is arguing about division of chores and childcare. The husband contends he works outside the home and should not have to take care of the house or children.