given elements ABCD, find the combination and the permutation with 3 elements.

ABC, BAC, CAB, DAB
ABD, BAD, CAD, CAD
CBA, BCA, CBA, DBA
ACD, BCD, CBD DBC
ADB, BDA, CDA, DCA
ADC, BDC, CDB, DCB

That is Permutation of set of elements ABDC with 3 elements, with regards in order.

ABC, BCD, CDA, DAB

That is Combination of set of elements ABCD with 3 elements without the regards in order