Seaweed is a term for edible marine algae harvested from the ocean; it overlaps with "sea vegetables" but refers specifically to algae rather than other edible coastal plants.
Seaweed has been a dietary staple in Chinese, Japanese, and Korean cooking for centuries and is now cultivated and harvested along coastlines worldwide. It carries a umami-forward, briny, sometimes slightly sweet flavor, with texture ranging from crisp and crunchy to soft and chewy depending on the species and preparation.
Common uses include sushi, miso soup, salads, stir-fries, Korean gimbap, Japanese wakame salad, and Chinese hot pot. It pairs well with citrus fruits, toasted nuts, and fermented ingredients.