system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Game Theory

After seeing the golden balls split standoff,  I understand what he did but don't understand the wider concept.
gpt
Game theory is a branch of math built around something called games. There are multiple players, and they each have some strategy to try to get the most points. You try to find something called the Nash equilibrium, where each player's strategy is the best possible strategy given their opponent's strategy.

For example, if you're playing rock-paper-scissors, if you always pick rock you opponent can beat you by always picking paper. If you always pick paper they can always pick scissors. And if you always pick scissors they can always pick rock. But there's a Nash equilibrium if you randomize it. If you pick rock one third of the time, paper one third of the time, and scissors one third of the time, then no matter what strategy they use, they'll win one third of the time, lose one third of the time, and tie one third of the time. If they're using that strategy too, then there's nothing you can do to be more likely to win, so that's the Nash equilibrium.

You can also look at subtle variations, like what happens if you count rock as two wins instead of one. In that case, you should pick paper half the time and rock and scissors one quarter of the time.

Also, games aren't necessarily zero sum. The Prisoner's dilemma is probably the most famous example of a non zero-sum game.