The document discusses seaweed. It begins by introducing seaweed as a type of marine algae that is multicellular, photosynthetic, and non-flowering. It then lists some common seaweed genera and describes seaweed structure. It notes that seaweeds are generally made up of a holdfast, stipe, and blade. It also outlines the three main types of seaweed based on pigmentation - red, brown, and green algae. The ecology and life cycle of seaweed is then summarized, noting their dependence on seawater and light. Finally, several applications of seaweed are listed, including as a food, in beauty products, and for potential medical benefits.