A convection oven is different from a traditional oven because of the fan that is built into the convection oven. This affects cooking time, temperature and how foods brown while cooking.
About.com explains that a convection oven uses a fan to circulate the heat, versus a traditional oven that does not circulate the air. The lack of air circulation in a traditional oven can lead to hot spots and uneven cooking; however, it is the best approach to cooking covered items like casseroles or stews. Foods that are cooked in high-sided dishes or with lids do not need the browning abilities that a convection oven has, and the high-sided baking vessels actually impede the air flow that a convection oven supplies.
The distribution of heat that a convection oven has makes food cook 25 percent faster and provides even cooking and browning of roasted meats, vegetables, cookies, cakes and other foods. This difference in cooking time can be compensated for by either reducing the cooking time or lowering the temperature by 25 degrees. Either reduction method helps to ensure that the items in the oven are evenly cooked without risking the quality or flavor of the food by overcooking it.