Kombu is a type of kelp or seaweed that originates from Japan and is an integral part of Japanese cuisine. This dark, leafy sea vegetable comes dried in thick, long strips, and is known for its umami flavor, a savory taste also referred to as the 'fifth taste' in food.

Kombu is used in a variety of dishes but is perhaps most renowned for its role in creating 'dashi,' a flavorful broth that forms the base of numerous Japanese soups and stews. It can also be used in salads, used for pickling, eaten as a snack, or used to flavor rice.

Health-wise, kombu is exceptionally nutritious; it's packed with essential minerals like iron, calcium, and iodine, rich in vitamins, and promotes good digestion.

Most importantly, when cooking with kombu, it is recommended to soak it in water until it softens, and then cook it over low heat to maximize its flavor. Typically, it is either removed after cooking or chopped and served with the dish. Make sure to store your dried kombu in a dark, cool place for the best shelf-life.

Kombu can usually be found in the international foods aisle of a grocery store, specifically in the Asian or Japanese section. You might also find it in the natural foods or seaweed section. If you cannot find kombu in your local grocery store, you can try a health food store, an Asian market, or purchase it online.