So – is that just a prefold and does it really catch everything that comes out of his bottom?

Yes it is just a prefold, and he would probably have a cover on if he hadn’t just made a poo. It actually does a great job of catching everything, though. My kids typically wear just a prefold when it is warm and we are about the house. I think a wet diaper next to the skin really helps with potty training when it’s time.