With temp ones they twist the intestine in a loop that's brought above the skin. It is possible for some waste to pass thru it with some people. During the take down surgery they untwist the loop and take it back down in with the rest of the remaining intestines.
With a permanent one they take the end of the intestine through the skin so it is the actual end point. That way no waste passes through anywhere but the stoma.
I had a horrible time with my temp/loop after the first colon removal/j-pouch construction surgery. I was in the hospital 16 days as I kept getting dehydrated. The ileostomy output was non stop. I hated that temp stoma but I've learned to appreciate this end one.