They habitually eat fish, octopuses, and crustaceans. They do not have many teeth on the edges of their jaws, but they have heavy crushing tooth plates inside the pharynx. They swallow prey rather than biting pieces off of them. The largest is the Atlantic goliath grouper ( Epinephelus itajara) which has been weighed at 399 kilograms (880 pounds) and a length of 2.43 m (7 ft 11 + 1⁄ 2 in), though in such a large group, species vary considerably. They can be quite large: in length, over a meter. They are not built for long-distance, fast swimming.

Groupers are teleosts, typically having a stout body and a large mouth. However, some of the hamlets (genus Alphestes), the hinds (genus Cephalopholis), the lyretails (genus Variola), and some other small genera ( Gonioplectrus, Niphon, Paranthias) are also in this subfamily, and occasional species in other serranid genera have common names involving the word 'grouper.' Nonetheless, the word 'grouper' on its own is usually taken as meaning the subfamily Epinephelinae. In addition, the species classified in the small genera Anyperidon, Cromileptes, Dermatolepis, Graciela, Saloptia, and Triso are also called 'groupers.' Fish in the genus Plectropomus are referred to as 'coral groupers.' These genera are all classified in the subfamily Epiphelinae. The common name 'grouper' is usually given to fish in one of two large genera: Epinephelus and Mycteroperca.

Not all serranids are called 'groupers' the family also includes the sea basses. Groupers are fish of any of a number of genera in the subfamily Epinephelinae of the family Serranidae, in the order Perciformes. For other uses, see Grouper (disambiguation).

Salmon grouper fish