When choosing 3 different elements out of 8 you have ( 8 ! ) ( 3 ! ) options.
This is called the number of 3-permutations of 8.
When choosing 3 elements out of 8 and their mutual order is not relevant there are ( 8 3 ) = 8 ⋅ 7 ⋅ 6 3 ! options.
This is called the number of 3-combinations of 8.