An amphibious assault ship (also referred to as a commando carrier or an amphibious assault carrier) is a type of amphibious warfare ship employed to land and support ground forces on enemy territory by an amphibious assault. The design evolved from aircraft carriers converted for use as helicopter carriers (and as a result, are often mistaken for aircraft carriers), but includes support for amphibious landing craft, with most designs including a well deck. Coming full circle, some amphibious assault ships now have a secondary role as aircraft carriers, supporting V/STOL fixed-wing aircraft. (source)