A snail shell is a hard, protective outer covering made primarily of calcium carbonate. It serves as a home for the snail, providing shelter from predators and harsh environmental conditions. The shell is typically spiral-shaped and can vary in size, color, and texture depending on the species of snail. Snail shells grow as the snail matures, adding new layers to the existing structure. The shape and pattern of the shell can help identify different species, such as the garden snail or the apple snail. These shells also play a role in the snail's buoyancy and mobility in their aquatic or terrestrial habitats.