Six Degrees of Kevin Bacon

Six Degrees of Kevin Bacon or Bacon's Law is a parlor game where players challenge each other to choose an actor whom they connect to another actor via a film in which both actors appeared: this is repeated to try to find the shortest path that leads to prolific American actor Kevin Bacon. It rests on the assumption that anyone involved in the Hollywood film industry can be linked through their film roles to Bacon within six steps.

Source: Wikipedia — Six Degrees of Kevin Bacon (CC BY-SA 4.0)