What is nutritional yeast?

It's an actual yeast that is heat dried and therefore deactivated. It has a kind of cheesy quality. It's delicious on cauliflower, kale, popcorn etc. You can get it at many grocery stores or health food stores. I get mine at Whole Foods in their bulk section. I like the flaked version. Brags also has it in a spice type container in powdered form.