There is a lot of hype around move to earn concept of tokens.
BUT I don't understand where does the money for the rewards come from? ''Who'' pays these rewards?
Try to spend a few minutes to read whole of explanation that already mentioned in the stepn whitepaper will be answering all of your question about that.
https://whitepaper.stepn.com/Can someone please explain that to me? THANKS!

It's fully explained in the whitepaper. I know you are answering a question but that whitepaper will be answering all of your questions.