It means there is no concrete starting point, and thus no place for a creator or creation event. It’s the fundamental upsetting of the Aristotlean metaphysical system.
Please note I’m not claiming that the Universe, at least in a temporal dimension, is a compact manifold. Certainly Classical Physics, which General Relativity sits firmly within, does not assert this. Quite the opposite, General Relativity gives a definitive starting point; though that starting point is a singularity, which isn’t an object or a moment, but rather a point at which the math breaks down and Einsteinian mechanics starts producing gibberish results. That indicates the math is insufficient to describe that region of space-time (much as GR breaks down when describing black holes). It’s entirely reasonable to assert an Aristotlean “unmoving mover”, but if one rejects those Classical notions (both the metaphysics and the Newtonian and Einsteinian physics represent), then we run into a communications problem. I can’t find appropriate language to describe space-time as a compact manifold, but I do know that it represents a notion of the Universe as self-contained, finite in all directions, but without boundary or starting point.