A permutation consists of the same particular set of numbers in different arrangements. Each arrangement is a separate permutation.
A combination consists of a set of particular numbers in no particular order.
There are more permutations than there are combinations. So (5,7,18,23) is the same unique combination as (23,5,18,7), but it's a different permutation (arrangement).
If the size of the set is always 4, then the number of combinations is 24×23×22×21/24=10,626.
The number of permutations is 255,024.