There is only the one genus in the family Haliotidae, and about four to seven subgenera. The number of species recognized worldwide is about 100.
The shells of abalones have a low and open spiral structure, and are characterized by several respiratory holes in a row near the shell's outer edge. The thick inner layer of the shell is composed of nacre or mother-of-pearl, which in many species is highly iridescent, giving rise to a range of strong and changeable colors, which make the shells attractive to humans as decorative objects, and as a source of colorful mother-of-pearl.
The flesh (the adductor muscle) of abalones is widely considered to be a desirable food.