One of the fundamental ingredients in Japanese cuisine, dashi is a type of soup and cooking stock often used as the base for different miso and noodle soups, donburi or rice bowl dishes, stews and many other kinds of nimono or simmered dishes.
Dashi is typically made from kombu (dried kelp), katsuobushi (dried and smoked skipjack tuna), iriko or niboshi (anchovies or sardines), or a combination of these ingredients, all of which are naturally rich in glutamates and thus deliver an intense umami flavor to a number of Japanese dishes.
It is most often used for preparing dishes such as miso soup, oyakodon, oden, nikujaga, chikuzenni, tamagoyaki, etc. Kombu dashi is a vegetarian stock made exclusively with kombu; it has a mild flavor and goes well with either vegetable or fish-based dishes such as yudofu or clamp soup, as it doesn't overpower other flavors. Iriko or niboshi dashi is a seafood-based stock made from dried baby anchovies or sardines; it has a strong fishy aroma, but its flavor is not as strong.
Compared to katsuobushi and kombu, this dashi is more affordable and most commonly used for making miso soup, noodle soup dishes like curry udon or kitsune udon, as well as various donburi and nimono dishes. Shiitake dashi is another vegetarian stock made by rehydrating dried shiitake mushrooms.