Seaweeds are macrobenthic (large and attached) forms of marine algae. They have a simplified, primitive structure compared to higher plants. The vegetative plant body, generally called "thallus," has no true roots, stems and leaves. They vary in forms. Some are branching, leaf-like or bushy type, club-like and featherlike, while some form sponge-like encrustations on hard substrates like rocks, corals and boulders. Seaweeds are generally photosynthetic plants. The three major groups of economic importance are Chlorophyta (green seaweeds), Phaeophyta (brown seaweeds) and Rhodophyta (red seaweeds).

In the Philippines, the different species cultured and collected are Eucheuma, Gracilaria and Caulerpa. The most popular and commercially cultured species is the Eucheuma cottonil because it is easy to cultivate and due to its fast growing characteristics and high market price.

Sixty-five percent (65%) of the total production are processed into semi-refined chips/carrageenan, (22%) are processed into refined carrageenan and the remaining (13%) are exported raw (dried).

The economic importance of seaweeds lies on its utilization in the food industry, pharmacy and medicine. Eucheuma is a source of carrageenan, a natural gun used as additive binder and emulsifier on food, pharmaceuticals, beverages and cosmetics. The major products derived from seaweeds are agar, algin or sodium alginate and carrageenan.