UUIDs are integers, they just happen to be 128 bits long instead of the more common 32 or 64, and they are usually printed in a specific way that differs from how integers are usually printed. But that's just smoke and mirrors.

UUIDs are generally not guaranteed to be universally unique. The name is misleading marketing.

If you generate them randomly, then the probability of collision is small enough not to matter, but the more you introduce deterministic elements, like generating them sequentially, the more your probability of collision increases.