Metric space

A metric space is like a playground. It has rules (called "axioms") that define what is allowed and what isn't. For example, if two points (players) are standing next to each other in the playground, they have a certain distance between them. Another rule might be that if two points are farther apart, then the distance between them is bigger than the distance between two points that are closer together. And if you want to know how far apart two points are, you measure the distance between them.