The simulation hypothesis is the idea that our reality is a simulation computed in another reality. In simpler words, the world is some kind of game universe and we are characters in the game.
I think that, on the one hand, the simulation hypothesis is a simple intuitive metaphor for a reality that is probably much weirder and hopelessly beyond our current imagination. But on the other hand, he simulation hypothesis is a coherent and useful mental picture of reality.
Picture by Extropia DaSilva. Perhaps the world is like Second Life?
(podcast) The simulation hypothesis