What does this mean and can someone give me an example for number 1 ?

Arandom number generator is used to model the patterns of animals in the wild this type of study is called

How many different three-digit numbers can be formed using the digits 1 comma 2 comma 9 comma 6 comma 4 comma 3 comma and 8 without repetition? for example, 664 is not allowed.

If you could answer these your a life saver