Recently I came across a concept which I thought was quite interesting- The Prisoner's Dilemma
It is a fundamental problem in game theory. It is a situation where two parties must choose to cooperate or not and where both gain when both cooperate, but if only one cooperates, other gains even more, while if both don't cooperate, both lose.
To explain it better, let's say there are two people- A and B who are caught for a crime. Both of them make an agreement that they will not confess the crime and remain silent. Now they are separated and questioned. So now, if both remain silent, they get 1 year in prison, if A cooperates (keeps the agreement) and remains silent but B confesses, then A gets 20 years in prison while B goes free and similarly the other way round if A confesses to the crime and B doesn't, then A goes free but B gets 20 years and in the case where both confess the crime, both get 5 years in prison.
This figure below might make it clear: