The trite answer is that both space and time were created at the big bang about 14 billion years ago, so there is nothing beyond the universe. However, much of the universe exists beyond the observable universe, which is maybe about 90 billion light years across.
Scientists measure vast distances in parsecs. A parsec is 3.26 light years, the unit used when the number of light years between objects climbs into imagined distances.
Alexander, 9, and I debated this question. He said the universe is infinite. I said it is not. I like to think of it as an expanding balloon and will prove it to him next time by way of metaphysics.