The Multiverse[]
A Multiverse is a theory of the world, supposedly many universes. There are theories about the multiverse. Some believe we're in a giant ocean of universes which is the multiverse. Some believe that in each multiverse, there's an alternate reality than ours, but also sort of similar. Some believe that a multiverse just doesn't exist. Beyond our universe light just hasn't traveled far enough to us to tell, even with the trillions of years in our universe.