Again, with a List this would not be required but an array's size is not directly corresponding to how many items it has, so we must track this ourselves
i in this case is purely for the for-loop to loop through the array. It increments until it is the same value as index, in which case it ends because the array would no longer have values
You use it to indicate where you place the next username/password, but you can also use it to indicate in the for-loop where it ends because there are no more usenames