According to general relativity there is no edge to the universe. Either space goe on forever or it closes back on itself, i.e. if you a straight ray returns to where it originated.
A universe is where space (or perhaps spacetime) exists. A non-universe is the absence of space (or perhaps spacetime).
Yeah well general relativity is wrong to assume this.
The universe as it is defined, has a diameter of 27 billion light years, right? Thus, we have Olber's bubble. Why we have Olber's bubble is probably because of redshift....very basic stuff here.
Now this is probably not the intended question of the OP. Indeed, what is at the edge of the cosmos is harder to answer.
The universe as infinite is only an interpretation, it's just a value we devised. You get rid of meta-cognition and you get rid of the problem with this infinity gibberish. Infinity can only ever be linear in concept, yet is the same as a point since undefined dimensionally, which proves extension.