system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Differences in cookie sheets

I baked the same cookies (trader joes break and bake) on two different cookie sheets with two different liners (dark nonstick with silpat vs light air gap with parchment paper). They turned out completely different. Can you explain the difference in cooking with the two type of sheets?
gpt
It is a matter of the heat distribution around the dough.

Imagine (or even try) putting a raw cookie in a skillet on the stove. Obviously the bottom will burn and the top will be raw. However, with a very low heat and a cover on the skillet you will get different results (the cover will help spread the heat, but you will also lose moisture at a slower rate).

Same idea happens in the oven depending on the cooking surface and placement in the oven and the relative heat distribution within the oven itself. A well insulated cookie sheet placed on the top rack will over bake the top of the dough and under bake the bottom. An uninstalled sheet placed on the bottom rack may burn the bottom of the dough before the top is finished.

You have to adjust/experiment to find perfection for your dough and equipment.