For example, imagine you are going to see a play at a theater. The theater is like the application, your gateway to the play, while the simulation is the play itself, defined by a program. You take your seat and you can see the stage, where the play will take place. When the play starts, the curtain rises and reveals a scene composed props and actors that then act out that part of the play. When it’s time to move to the next scene, the curtain falls, the scene is reset, and then the curtain rises again, revealing the next part of the play. The stage crew and all the mechanical devices behind the scene that manages the curtain and the props is the world of the play.