what's the difference between permutations of subsets and combinations?

Answer 1

As far as definitions go, the answer is pretty simple: a permutation is a particular set in a particular order, where a combination is just a particular set.

An example probably isn't necessary, but take a subset of {1,2,3,4,5}, say { 2,4}.

{2,4}, or {4,2} are one combination, but they're two permutations.