The "Universe" generally refers to one of any number of infinite spaces that exist parallel to each other or within different dimensions, but most commonly refers to one in particular. You know the one we mean. It's the biggest and therefore the best, and its inhabitants are just stuck-up enough to take the generic title for themselves.
This universe, the main one by its own definition, began with a Big Bang at the location where the planet Eternium currently sits, which is therefore considered its exact center. Technically there is no exact center because it's an infinite space, but just go with it. Since that point it's been expanding outward at an ever-increasing rate. Technically that's impossible since it's an infinite space to begin with, but just go with it.
Like all things, the universe is mortal and can't last forever. A very successful catering venture, Milliways (a.k.a. the Restaurant at the End of the Universe) has been set up at the exact time when the universe meets its fiery end, allowing patrons to witness the cataclysmic apocalypse from a safe distance while enjoying Ameglian Major Cow.