A Schelling focal point is a concept from game theory that allows two people unable to communicate with one another to coordinate a decision.
As an example, imagine that you are shown a series of four squares of different sizes; three red and one blue. You are asked to pick the square that your unknown partner will pick, with the assumption that if you pick the same you will both receive an award.
If you’re smart, you pick the blue square, because it most prominently signals singularity.
The idea is not purely academic. People use focal points all the time.
For instance, suppose you get separated in a Mall and have no way to contact a person. Assuming you don’t have any personal information about a person that allows you to guess where they would be, where do you go to meet them: in front of Sears, or in front of the central carousel? The carousel, obviously. It’s the blue square in an ocean of reds.
Suppose you are supposed to meet someone in New York you have never met, and somehow the instructions to meet get garbled. Could you meet them?
Schelling’s original examples involved something like two people told to find each other in New York. You might think this would be impossible, but people often succeed by choosing a psychologically salient time and place — say, the Empire State Building at noon. What’s interesting about this is that they may not even perceive this meeting point as a choice: person A has to do it because he or she thinks person B will do it, and vice versa. (Source)