well, if you're talking about different styles of Chinese food, generally there are four schools:
Northern
Based in North China, this cuisine uses wheat as a staple rather than rice. Oily, dark textures and large, filling dishes of noodles, dumplings or meat help the Northern Chinese shiver through cold winters.
Western
The most famous variant of this school is based in Sichuan Province (Where I am right now!) the food has a lot of peppercorns and spices in it, a lot of things are very spicy and can give you heartburn quite easily if you're not used to it. Very strong, very distinct flavours.
Eastern
Not quite as distinguished as the other three "schools", Eastern China based around the mouth of the Yangzi (Shanghai, Nanjing, etc) tends to also use oils, salt and a lot of sweet sauces in their foods. Popular choice in winter.
Southern
Based around the steaming semi-tropical coastline of Canton and Hong Kong, this cuisine prefers to bring out the natural flavours of ingredients. Relatively little oil is used, and seafood is quickly steamed with only a hint of ginger perhaps. Has wide variation of ingredients. Most western "Chinese" food has its origins here. (Although the HK/Canton version of course is WAYY better) Believe it or not, sweet and sour pork does exist here, but it is ordered relatively rarely and is "balanced" out with a veggie dish usually. Dim Sum also comes from this area.
I'm not overly familiar with regional variations in Japanese food, I would find that a very interesting topic. I only know Sushi came out of Edo (Tokyo) and that Okonomiyaki, Tako-yaki and battera sushi (sp?) came out of Osaka. Also the bottomless Soba from Tohoku and the Ruibe sashimi from
Hokkaido. (I loved the way a book described Ruibe: "Take a salmon and leave it in the snow of a Hokkaido winter. Wait. Enjoy".)
Anyone want to enlighten me?