The term "baking" is often used to refer to oven cooking, but this definition isn't completely accurate. Baking actually means cooking something uncovered with dry heat and it's hands-down the best method for baked goods and most meats. You can cover almost any other food as it cooks in the oven to keep it moist.
Baking is a dry heat method -- typically at a moderate temperature around 350 degrees Fahrenheit -- that causes foods to become browned on top. Baking generally refers to the cooking method for making cookies, breads, muffins and cakes. Roasting is similar, but the temperature is often much higher. Meats and vegetables are typically roasted. Any time you cover a dish with a lid or foil, you're no longer baking, but steaming, braising or poaching. Added liquid, or even liquid present in the food, condenses and keeps the food moist. These methods are moist heat methods.
In almost every case, you'll bake cookies, pies, breads and other baked goods uncovered. Leaving the baked goods uncovered allows them to develop a golden brown crust and encourages them to rise. If the baked good begins to brown before the inside is done, you can loosely place a piece of foil over the baked good. This is especially true for pies and brownies, in which the edges brown before the center is done. Occasionally, a recipe calls for steaming a cake or heavy pudding. In this case, you would cover the dish.
Casseroles and Meats
Casseroles, such as lasagna, are often cooked covered for part of the cooking time to prevent dryness. The cover may be removed at the last minute to allow cheese or toppings to brown. When it comes to meat, leave the cover off when roasting tender cuts of meat. Cover meats and add some liquid if the meat is a tough cut that needs tenderizing. This method is also ideal for quickly cooking fish and chicken breasts.
The Bottom Line
Here's a simple rule to help you remember: When you want a golden crust, bake foods uncovered. This method slightly dries food, which in certain instances is desirable. If you don't want browning, but you want moisture and tenderness, cover the food. When using a convection oven, you can bake food either covered or uncovered. However, convection ovens are particularly useful for roasting meats and baking cookies, breads and cakes uncovered.