Compounding interest is interest on top of interest.
For example, say you put 100 bucks in the bank.
You get 10% interest compounded daily on that 100 bucks.
That means that you get 10% interest not only on those 100 bucks, but all the money you make after.
So your interest would go from 10% on 100 bucks, to 10% on 110 bucks and so forth.
I hope this helps and please press that ❤ under my reply, it really helps!