A crab is a type of crustacean that usually has a hard shell, ten legs, and pincers. They can be found in oceans, rivers, and even on land. Crabs are known for their sideways walk and are often seen scuttling along the beach. They come in many varieties, such as the blue crab and king crab, each with unique features and habitats. Crabs are not just interesting to watch; they are also a popular food choice in many cultures. People enjoy dishes like crab cakes and crab legs, which are considered delicacies. Additionally, crabs play an important role in the ecosystem, helping to keep marine environments healthy.