Role-playing is a game. For this game you need at least two people, usually 3-5 people. One person will be the storyteller. The other people will play the game as a character they will control. The storyteller controls everything else in the game. As with any game there are rules. And the one rule that is true in all role-playing games is: whatever the storyteller says goes. Other than that all role-playing systems differ in how they use rules to represent a fictional world.