Stir frying is a common Chinese cooking technique used because of its fast cooking speed. Cantonese restaurant patrons judge the chefs by their "wok qi" (their ability to bring out the qi of the wok, which shows in the food as the look, smell, and taste). A traditionally round-bottom pan called a wok is heated to very high temperature. Then, a small amount of oil is poured down the side of the wok (a traditional expression in China regarding this is "hot wok, cold oil"), followed by seasonings, meats, veggies, rice and/or noodles. In some dishes, different components will even be stir fried separately before being combined in the final dish (if, for example, the chef desires the taste of the stir fried veggies and meats to remain distinct).
The food is stirred and tossed very quickly using wooden or metal cooking utensils. Some chefs will lift the wok to the side to let the flame light the oil or add a dash of wine spirit to give the food extra flavor. Using this method, many dishes can be cooked extremely quickly (within a minute).
Some dishes that require more time are cooked by adding a few dashes of water after the stirring. Then the wok is covered with a lid. As soon as steam starts to come out from under the lid, the dish is ready. In this case, the food is stir fried on high heat for flavor and then steamed to ensure that it is fully cooked.
Most home kitchens in the West are never equipped to handle the large amount of oil vapor produced as a byproduct of proper stir frying, and thus stir frying in those kitchens often cannot achieve the same great flavor as in restaurants mainly because the wok is not hot enough and is too small to allow fast tossing. By contrast, most Chinese home kitchens are designed with stir frying in mind. The kitchen itself is either in a separate building or in a room with access to the outside. The stove is usually near a large window to allow for ventilation and separated from the rest of the kitchen. The kitchen itself usually is lined with tile or brick for easy cleaning. Many western cooks on TV demonstrate stir frying on low heat with a small wok and a stirring motion comparable to tossing a salad. This is a western adaptation of stir frying, but it is dissimilar to the traditional Chinese method.