When a Japanese refers to 海苔 it can mean several things. Here are some of them.

海苔（のり）Nori (Japanese Seaweed)

Baked nori. 
This is the most common one used to wrap onigiri or sushi.

Seasoned nori.
Seasoning ingredients vary from salt, soyu, sesame oil, or sugar. This is one option for a healthy snack.

Shredded nori.
This kind of nori is frequently used as topping on a soba or udon dish. I once found shredded nori as filling, though, inside bread together with buttercream.

Nori flakes.
You'll probably find it as garnish on your okonomiyaki, or yakisoba, or takoyaki.

Natural nori.
This is rare type that grows naturally on rocks. And yes, 岩 means "rock".