Oriental cuisine can actually refer to very different styles of Asian cooking depending on the nation or area. The Oriental section of Asia covers a huge chunk of eastern Asia known as the Far East, and thus encompasses a wide range of culinary traditions. What might be called Oriental cooking in one nation might be considered something else in another nation.
The geography of the area that makes up "the Orient" stretches from east Siberia south all the way to Indonesia and includes Mongolia, Japan, Korea, Vietnam, Thailand and most of China. Oriental cuisine almost always refers to some type of Asian cooking from the Far East region, eliminating most dishes from Siberia and Indonesia.
There are many types of Chinese cuisine, because different areas of China can have distinctly different styles of cooking. Many times when someone in Europe or America thinks of Oriental food, Chinese food comes to mind, with its use of chicken, rice, vegetables, sauces and exotic ingredients. Chinese food qualifies as a type of Oriental cuisine.
Japanese cuisine also is a type of Oriental cuisine. Japanese culinary tradition makes heavy use of fish, as well as sushi and other seafood. This cooking has a very distinct taste and style compared to many other types of Asian cooking from the Far East area, because there is less frying and more careful preparation of steamed or even raw foods.
Korean cuisine is another form of Asian cooking that can fall under the umbrella term of Oriental cuisine. Kimchi, a very popular dish, involves putting rotting vegetables in a stew and burying the stew pot to make it ferment. Rice, noodles, seaweed and snails are also used in Korean cuisine, and Koreans' spicy barbecue is beginning to catch on.
Cuisine from Southeast Asia also qualifies as Oriental food, with Thai and Vietnamese being the two that are most well known in Western nations. Various noodles, curries and hot spices help distinguish Southeast Asian cooking from that of some of the other Oriental nations that make up the Far East.
While Oriental cuisine is a broad term that can cover many styles of cooking, what exactly falls under "Oriental" can also depend on the location. In many parts of Asia, there are still advertisements for "Asian food," but in China this might mean Korean or Japanese food, while in Vietnam it might mean Chinese or Japanese food, and in Japan it could mean Thai or Mongolian. From that standpoint, what exactly counts as "Oriental" in Asia varies by country.