A crustacean is a type of animal that belongs to the class Malacostraca within the phylum Arthropoda. These creatures are characterized by their hard exoskeleton, jointed legs, and segmented bodies. Common examples of crustaceans include crabs, lobsters, and shrimp. They are primarily found in aquatic environments, both in oceans and freshwater. Crustaceans play a vital role in the ecosystem as they are important food sources for many animals, including fish and birds. They also help in the breakdown of organic matter, contributing to nutrient cycling in their habitats. Many people enjoy eating crustaceans, making them significant in both culinary and economic contexts.