Coral species are generally divided into two subspecies, depending on how many tentacles the coral individual has. Those coral species with eight tentacles are known as Alcyonaria, which includes soft coral, sea fans and sea pens. Those coral species with more than eight tentacles are known as Zoantharia, which includes the coral species that are found in coral reefs.

The coral catches small fish and animals such as plankton using stinging cells on their tentacles, although these animals obtain most of their nutrients from algae. This means that most corals depend on sunlight and grow in clear and shallow water, typically at depths shallower than 60 m (200 ft). There are however a number of coral species that have adapted to inhabiting the oceans at depths of up to 3000 m.

Corals can live from 3 months to 30 years depending on the individual coral species and the role it plays within the eco-system. For example, those coral species that make up the extensive coral reefs (like the Great Barrier Reef in Australia that stretches for over 1,600 miles in length) tend to live alot longer than those species which are found on their own, like the softer corals.