Ramen was imported from China to Japan, and evolved in its own way in Japan. Ramen eaten in Japan largely falls into the following main categories depending on the kind of soup: soy sauce ramen, salt ramen, miso ramen, Tonkotsu ramen(pork bone stock), seafood ramen.
Many restaurants also offer the tsukemen ("noodle dipping") style, where noodles and soup are served separately.
There are also restaurants offering ramen for vegetarians and/or Muslims, although they are rare.
The flavoring of the soup, the type of noodles, ingredients and so forth differ from restaurant to restaurant.
Ramen restaurants tend to compete on the basis of the restaurant's distinctive character, so there are a wide variety of flavors to enjoy.