To astronomers, the "universe" is the collective name for everything produced by time, space, matter, and more. In philosophy, it is also called the world. But this is merely the limited perspective of humankind's tiny realm of study.
Stretch your perspective infinitely, and the once-vast, boundless universe becomes like a "leaf." It feels as if a light squeeze would crush it with ease. Countless leaves like it fill the surroundings, their roots connected to a vast tree beyond words, real or illusory, in which all abstract concepts converge. The "Tree of Infinity" is the origin of the universe, and the end of all universes.