Anglerfishes are members of the teleost order Lophiiformes /ˌlɒfiːəˈfɔrmiːz/. They are bony fishes named for their characteristic mode of predation, wherein a fleshy growth from the fish's head (the esca or illicium) acts as a lure like the one found in angling.
Anglerfish occur worldwide, some are pelagic, others benthic; some live in the deep sea (e.g., Ceratiidae) others on the continental shelf (e.g., the frogfishes Antennariidae and the monkfish/goosefish Lophiidae). Pelagic forms are most laterally (sideways) compressed whereas the benthic forms are often extremely dorsoventrally compressed (depressed) often with large upward pointing mouths.
From : http://en.wikipedia.org/wiki/Anglerfish