It is a fascinating subject, probably the most fascinating subject, as physicists attempt to put together a theory of everything.
The fact that you would get a set of completely different answers to your question from leading physicists around the world just goes to show how little we know (despite our advances in recent times).
For what it's worth, and i'm no physicist just a someone with a keen interest, I don't subscribe to the parallel universe theory. The idea that there are an infinite number of replicas of us accounting for every single possible outcome of a given event is ridiculous in my opinion. I'm warming a little to the multiverse theory, although still not totally convinced. I could see our universe acting as a satellite (on a much grander scale), as we know satellites are part of the make up of objects in our universe on all scales.
The Hubble Space Telescope has paved the way for a greater knowledge of the universe, a magnificent piece of engineering. I just hope it's successor, The James Webb Space Telescope, isn't scrapped as it it promises an exciting new era of understanding.