Seaweed is a generic term for about a dozen different kinds sold at Asian stores, all of which are not vascular plants but multicellular algae. The more common ones, already mentioned are kombu, wakame, and nori. They are very different; in fact, from entirely different plant genus.
Kombu is of the same genus (laminaria) as the giant kelp of Monterrey Bay. They are thick, like cardboard, and come packaged in large dried strips. They’re tough. To eat, they’re usually braised.
Wakame is an undaria usually packaged in crumpled little dried bits. When reconstituted, they expand to irregularly torn, very thin, almost translucent, sheets anywhere from fingernail to palm size.
Nori is a prophyra biofilm algae, gathered and compressed into thin dried sheets. Available seasoned.
For wakame seaweed salad, the one that first comes to most people’s mind is mixed with paper thin slices of cucumber and some very finely julienne ginger. One part soy sauce to two parts rice vinegar. Some people dilute it with the addition of dashi broth. Others also might thicken it with a pinch of starch.