A permutation is a configuration of a set. All the permutations for a given set of items are
therefore all the possible different configurations of that set.

Take the following set: "abc". One permutation of "abc" is "acb".
Mathematically speaking, the number of possible permutations for a given set is N!, or the factorial of the
number of items in the set. "abc" is a set of three items, so its maxiumum number of permutations is 3!

Explicity written, the total possible permutations of "abc" = 3 x 2 ∴ 6

The total possible permutations of "abcd" = 4 x 3 x 2 ∴ 24