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 sizes and colors, with some species being quite small while others, like the King Crab, can be very large. Crabs are not just interesting to watch; they are also an important part of many ecosystems. They help keep the ocean floor clean by eating dead plants and animals. Additionally, crabs are a popular food source for humans, with dishes like crab cakes and crab legs enjoyed around the world.