Casserole, by definition, refers to the pan your food is cooked in and then used to serve said food, from oven to table with one dish. Most often though, especially here in America, casserole is what we refer to as the food itself. Casseroles are often made in colder winter months. They are considered a comfort food, warming you from the inside out. Plus, we often don’t want to use the oven much when it’s hot outside. So, in winter it is by default.