I know when and where to use the multiplication principle.

"If one operation can be performed in r different ways and another operation can be performed in s different ways, then the number of different ways in which the two combined operations can be performed is r ! s."Can someone tell me where should I use the power principle (I don't know what is actually its name 2^3, 2^8 etc) and also the factorial (2!, 5! etc)

CB