In steaming, water is boiled continuously to produce a steady amount of steam. The steam surrounds foods and cooks evenly while retaining moisture. Steaming can be performed in a few different ways. For high-volume kitchens, a commercial steamer or combi oven is the most efficient. Other methods of steaming include using a pot and steamer basket, using a microwave, or wrapping foods in foil so they can steam in the oven.

Source: Webstaurant