What's the difference between arc4random and arc4random_uniform in Swift?

So I've seen old posts about the difference between random and arc4random in Obj. C, and I've seen answers to this online but I didn't really understand the answers so I was hoping someone here could explain it in an easier to understand manner.

What is the difference between using arc4random and arc4random_uniform to generate random numbers in Swift?

Thanks, Brennan