Nori (海苔) is a dried edible seaweed used in japanese cuisine, made from species of the red algae genus pyropia including p. yezonesis and p. tenera. it has a strong and distinctive flavor, and is often used to wrap rolls of sushi or onigiri (rice balls). the finished dried sheets are made by a shredding and rack-drying process that resembles papermaking. they are sold in packs in grocery stores for culinary purposes. since nori sheets easily absorb water from the air and degrade, a desiccant is needed when storing nori for any significant time.

Source: Wikipedia