Question 960965
With combinations the order does not matter whereaas with permutations it does.
Some examples should make it clear.

How many different combinations of 2 letters are there in  the letters a,b,c,d and e.

we have 10 : - (a,b) , (a,c) (a,d) (a,e) (b,c),(b,d), (b,e) (c,d) (c,e) (d,e)

- the order of each pair does not matter - we could write (a,b) as (b,a).

Howevet permations do require order to matter - so there are 20 permutations of 2 in the 5 letters.

The 5 actors in a group of 9 you mentioned are combinations - nothing is said about the order of each group of 5.