The Japanese thin dried seaweed used for wrapping sushi is nori. It is usually made from red algae in the genus Pyropia and pressed into dark, paper-thin sheets.
Nori is wrapped around sushi rolls and is also used to hold onigiri, Japan’s rice balls. Its savory, slightly oceanic flavor becomes crisp when toasted; toasted nori is called yaki-nori. Small flakes or strips may also garnish noodles, soups, rice, and furikake seasoning.
The sheet-making method developed in Edo-period Japan around 1750, using a process resembling papermaking. Nori has a much older culinary history: written records from the 700s describe it as food and even as a form of taxation.
Nori is often confused with kombu, but they are different seaweeds used differently. Kombu is a thick kelp primarily used to make dashi broth, while nori is the familiar wrapping seaweed.