Perciformes, whose name literally means 'perch-shaped', are the most diversified and heterogeneous group within the fishes and the order with the largest number of species among the vertebrates, accounting for up to 41% of all fish species according to the taxonomic classification used. The diversity of species within this order is so great that we will find both freshwater and saltwater species, in the vast majority of biotopes (open water, reefs, prairies, sand, mud, rocks, ...).

Although it is an order difficult to define due to the absence of clear distinguishing characteristics, we can say that Perciformes generally have a dorsal and anal fin with the first rays transformed into sharp spines that vary in number depending on the families, genera and species; and the posterior portion of these fins with soft rays. Generally the pelvic fins, which are located in a position between the throat and the belly, have a spine and up to 5 soft rays. The caudal fin usually consists of 17 or fewer main rays; while they have no adipose fin. The skin of Perciformes is covered by scales. The size range of the Perciformes ranges from 7 millimeters for Schindleria brevipinguis to over 5 meters for the Atlantic blue merlin (Makaira nigricans).

The classification of Perciformes is a rather controversial aspect, in which there have been numerous changes, and where genetic discoveries are allowing the reclassification of numerous families within and outside this order. Within the order Perciformes the more than 2,200 different species are organized in 2 suborders (Percoidei, Notothenioidei), with 62 families (54 and 8 families respectively) and 365 different genera.