An octopus has eight ARMS, which are referred to as tentacles, and no LEGS. An octopus is a cephalopod mollusk, meaning it is a soft-bodied, aquatic invertebrate with a distinct head and eyes. It is known for its eight ARMS, which are equipped with suction cups and can be used to catch prey or move around. The ARMS are also referred to as tentacles, and they are much longer than the octopus's three ARM-like appendages.