Filamentous or membranous multicellular red algae. Most species live in coastal water, but some freshwater species are also know. Porphyra is very important for food and cultivated especially in East Asia.

Cells possess a single (to few) stellate chloroplast. Golgi apparatus is associated with mitochondrion. Main compornent of cell wall is β-1,4-mannan in gametophytes and β-1,3-xylan in sporophytes. Egg on gametephyte forms carpospores after fertilization with spermatium. The carpospore germinates into sporophyte (Concocelis stage). The sporophyte produces conchospores via meiosis. The conchospore developps into the gametophytes. The gametophytes are also reproduced by monospores asexualy.