Hey desriix!
I was away for a while, since it was Carnival here in Brazil.
A permutation table is a randomly ordered list of values with one ocurrence of each value only. For instance, a permutation table with 6 values could look like [1,3,0,5,2,4]. So, if you get the permutation table values in order (1, then 3, then 0...) and use them as indexes for your questions array, you would be actually getting all questions in the array without repetition, in a random order. Is it clear?
Check this example and let me know if you have any doubts.
Cheers!