Consider the Prisoner's Dilemma, a classic scenario used to explain game theory.
Imagine that there are two partners in crime being interrogated in separate rooms. If one snitches, he goes free, but the other goes to jail for 10 years. If both stay quiet, they both go to jail for 2 years. If both snitch, they both get 5 years. Since they can’t coordinate, how do they decide what to do in order to minimize personal loss?