With nCr, order does not matter. With nPr order does matter.
Here is an example I like to use.
Say you have a combination lock. When you turn the dial, the numbers have to be in a particular order. That is a permutation.
If the numbers to open lock were, say, 1-13-25-31.
If it were a combination, you could enter them in any order and it would open.
With a permutation, they have to be in that particular order.
That is why they should be called permutation locks and not combination locks.