Question

Which type of loop is best in each situation?

For or While : You know ahead of time how many passes you wish to make through a loop.

For or While : You do not know ahead of time how many passes you wish to make through a loop.

Answer 1

If you know how many passes you'll be making, a for loop is most suitable.
If you do not know ahead of time, the while loop is better, since the while condition will decide if you're going to make another round.