Question

What is “permutation” and “combination”

Answer 1

Here’s an easy way to remember:
Permutation sounds complicated, doesn’t it? And it is. With permutations, every little detail matters. Assume your friends Alice, Bob and Charlie to be at 1st, 2nd and 3rd position respectively after winning a game. If they stand in a different order, say- Charlie, Bob and Alice, will it be acceptable. Obviously no. Because someone will get someone else's prize.
This is permutation, where order matters.
Combinations, on the other hand, are pretty easy going. The details don’t matter. Alice, Bob and Charlie is the same as Charlie, Bob and Alice, when they are standing anywhere randommly.
Permutations are for lists (order matters) and combinations are for groups (order doesn’t matter).
In other words- A "combination lock" should really be called a "permutation lock". The order you put the numbers in matters. (A true "combination lock" would accept both 10-17-23 and 23-17-10 as correct.)