Six degrees of separation is the idea that any two people on Earth are connected by at most six social steps or acquaintances.

This concept means you could start from yourself and reach any other person by going through a chain of no more than six friends of friends. For example, you might know someone, who knows someone else, and so on, until you reach the other person in six connections or less. This surprising closeness is called the 'small world' phenomenon and shows how tightly connected our social networks are.