What is the difference between a stew and a casserole?

This is a great question as when you master the basic cooking techniques and styles of cuisine, you can innovate. A stew is cooked in a heavy large pot on a stove top. The meat is browned in oil and the chopped vegetables are added along with enough liquid (wine, water, chicken or beef broth, milk or cream, or a cooking soup like cream of mushroom) to cover everything. One usually adds a starch like rice, pasta or potatoes too. These do not need to be precooked as they will cook during the hour or more that it simmers. They are simmered at a slight bubbling rate over an hour or more. Everything is done in one one large pot all on the stove top. It is simple but slow. Whether you cover it or not depends on how much you want to reduce the liquid and how hot you want it to get.

A casserole is made in multiple stages which ends in baking in an oven. First the meat for the casserole is browned on top of the stove in a frying pan along with onions and garlic in oil and or butter. Add browned meat to casserole dish. Then the main vegetables are chopped, sauted in a frying pan and added to the meat in the casserole dish. The the sauce is poured over the vegetables and meat. Cooked or uncooked rice, potatoes, and cooked or uncooked pasta (depending on size and shape) is also added to the casserole dish. Then the dish is topped with cheese, bread crumbs and dotted with butter or drizzled with olive oil. They are usually baked at 350 degrees for a hour or more. Here, whether it is covered or not with aluminum foil or a lid depends on how much you want it to reduce the liquid and how moist you want it to be on top and the sides.

A stew is cooked on a stove or over a fire and a casserole is cooked evenly in an oven. As well, casseroles are cooked either covered or not, while stews are usually covered so they don't evaporate.