Teleostei is a diverse group of bony fish that make up the largest class of vertebrates. They are characterized by a fully developed bony skeleton, a swim bladder for buoyancy, and a wide variety of body shapes and sizes. This group includes familiar species such as salmon, tuna, and goldfish. Teleosts are found in nearly all aquatic environments, from freshwater rivers to the deep sea. They play crucial roles in ecosystems as both predators and prey, and many species are important for human consumption and recreational fishing. Their adaptability has allowed them to thrive in various habitats around the world.