when do you use a combination and when do you use a permutation?

Question

owlfred · Answer

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anonymous · Answer

when the order of choosing some samples does not matter then we choose combination when order matters them permutation

anonymous · Answer

If the order doesn't matter, it is a Combination.If the order does matter it is a Permutation.In other words:A Permutation is an ordered Combination.
Permutations are for lists  and combinations are for groups