In taxonomy, Corals are in the Kingdom Animalia, Phylum Cnidaria(formerly Coelenterata). The Class of Cnidaria is known as Anthozoa which refers to "flower animals". They are not flowers although their bright coloration and the fact that they are sessile makes them seem like flowers. Anthozoa can be subdivided into subclass Alcyonaria into Orders Alcyonacea and Heliopooracea as well as Subclass Zoantharia and its Orders Antipatharia, Corallimorpharia, Scleractinia, and Zoanthidea. These can be divided further into families, genus and species. Some are stony and some are soft corals In Cnidaria, particularly in Coral, members are sessile(remain attached) and called polyps. The coral animals live in colonies of polyps and their calcium carbonate exoskeleton becomes a reef. The animal inside has a soft body with radial symmetry. It contains tentacles around a mouth, which takes in food particles. Corals breed asexually but also sexually. Gametes(sperm and eggs) are released into the water and form zygotes(fertilized eggs).
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.