A crustacean is a type of aquatic animal that belongs to the class Malacostraca within the phylum Arthropoda. They are characterized by their hard exoskeleton, jointed legs, and segmented bodies. Common examples of crustaceans include crabs, lobsters, and shrimp. Most crustaceans live in water, but some can also be found on land. Crustaceans play an important role in aquatic ecosystems as both predators and prey. They are a vital food source for many animals, including fish and birds. Additionally, crustaceans are significant in human diets and are harvested for their meat in various cuisines around the world.