A starfish, also known as a sea star, belongs to the class Asteroidea, making it an echinoderm, a type of marine invertebrate. Starfish are characterized by their star-like shape, typically having five or more arms radiating from a central disc. They are commonly found on ocean floors, where they inhabit various environments, including coral reefs and rocky shores. Despite their name, starfish are not fish and do not possess a backbone; instead, they have a tough exterior made of calcified plates. Starfish are also known for their regenerative abilities, allowing them to regrow lost arms.