Imagine you have 3 colored balls: red, blue, green. If you line them up in a row, is red-blue-green the same as blue-red-green?
No. The order is different. When order matters, each arrangement is distinct. This is a permutation.
If you only care which balls you picked (not the order), then red-blue-green and blue-red-green are the same. That's a combination. In this section, order always matters.