Nutritional yeast is a deactivated form of yeast that is popular in vegan cuisine for a number of reasons. One, it's often fortified with B12 and other nutrients that are important to include in a vegan diet. It also has a nutty, savory flavor which is very helpful when veganizing cheese, eggs or meats in a recipe, and it's great when sprinkled over popcorn!
Where do I find nutritional yeast?
Some conventional groceries may stock nutritional yeast in the seasoning aisle, or you may even be able to find it with the vitamins, but your bet bet is a natural foods store. Be sure you're getting the right type of yeast - it should look like a golden yellow powder, preferably with flakes.