What is a zero-sum game?

A zero-sum game is generated when the gain or loss of each of the members of the game is balanced with the losses or gains of the other players.

This means that by adding all the gains and all the losses, the final result will always be zero.

In conclusion, for a player to win, the opposing player must necessarily lose.

A zero-sum game is a game in which nothing changes, you don't gain anything nor do you lose anything.