A "parchment sheet" refers to a thin and durable piece of paper made from the skin of animals, like sheep or goats. It was commonly used in the past for writing or drawing purposes instead of regular paper. Full definition
One thing I did after baking the first side was to pull the cookie sheet with parchment out and put the second parchment sheet back over top of the crackers. (detoxinista.com)
Fold parchment sheets in half and use scissors to cut halves into 4 large hearts. (epicurious.com)
Slide the dough / parchment sheet onto a flat baking sheet or on the back of a rimmed baking sheet. (foodnetwork.com)