The deal is it works by treating numbers as numbers,I suppose you could imagine it as the larger numbers floating to the top of the list.Because there is no comparison between members of the list the time taken increases linearly rather than as the square of the number of items to be sorted so it youve got 1000 numbers to sort it takes 1000 operations compared to 1,000,000 with quicksort in the worst case.But as the numbers get bigger you need increasingly more memory to store the array.