Mushroom Flake? Butterfly Flake? What's all this flake-y talk? It's not snowing around here!
A "flake" is a piece of popped popcorn. It's popcorn farming jargon going back a ways. You can find both of the major types of popcorn flakes on JustPoppin.com - butterfly flakes (like Movie Pop and Tender Pop) which have bits that stick out (and sort of look like a butterfly) click here for more info, and mushroom flakes which are round, firm, and have few if any bits that stick out, which you can read about here.