Collusion and game theory play important roles in markets with only a few big companies, called oligopolies. They change how these companies act and interact with each other.

1. Collusion:

   • Sometimes, companies team up to decide on prices or how much they should produce.
   • This teamwork lowers competition and makes their profits go up.
   • A good example of this is OPEC, an organization in the oil market that works together to control prices.

2. Game Theory:

   • This is a way to understand how companies will react to each other's choices.
   • A well-known example is the "prisoner's dilemma." It shows that when two competitors choose not to work together, they might end up hurting their own profits if they push too hard against each other.

In short, these ideas create a complicated mix of strategies that affect how prices are set and how much products are made in oligopoly markets.