A cephalopod is a type of marine mollusk belonging to the class Cephalopoda, which includes species such as octopuses, squids, and cuttlefish. They are characterized by their bilateral symmetry, a prominent head, and a set of arms or tentacles equipped with suckers. Cephalopods are known for their advanced nervous systems, complex behaviors, and ability to change color and texture for communication and camouflage. They are highly adaptable and play significant roles in marine ecosystems.