Silpat is a liner made of silicone and fiberglass which replaces the need for parchment paper. It also produces a softer heat than baking right on a metal pan so your cookies won't overcook on the bottoms. The non-stick surface allows baked goods to slide off the mat after baking without the need for a spatula. You could also us it as a non-stick surface for rolling out sticky doughs or candies.It is freezer and microwave safe but you should never cut on it. And you need to store it flat or rolled up (I keep mine in the box). You'll be able to bake 3,000 batches of cookies on it before it wears out. That's a lot of chocolate chips!! Measures 11 5/8" x 16 1/2" to fit a 13" x 18" pan.