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Each class and subclass of mollusks exhibits a vast range of morphologies, although they all share certain essential traits. The muscular foot is the primary locomotive component. The visceral mass houses the majority of the internal organs. There is a tissue fold known as the mantle that covers the visceral bulk. Gills, which are respiratory organs, are located in the mantle cavity and normally cover the visceral bulk. Except for bivalves, all mollusks have an abrasive tongue-like structure termed a "radula" that serves as a unique feeding organ. Most mollusks lack a calcium carbonate-reinforced shell, but the Cephalopoda class, which includes squid and squid, has a significantly decreased amount of this shell.

The mantle is the limiting dorsal organ that lies above the visceral mass, while the muscular foot is the most ventral organ. Depending on the type of mollusk being investigated, the foot's structure and function can differ. It is used for both movement and anchoring. The leg of molluscs without shells is often the same size as the entrance of the shell. The leg can be extended farther. The foot of members of the class Cephalopoda, which means "head-foot," is funnel-shaped to rapidly discharge water from the mantle cavity, and the front border of the leg has been altered to form a circle of arms and tentacles.

Most molluscs have a special feeding organ, the radula, which has chitinous saw-like teeth. The radula is present in almost all groups. Used to crush or scrape food before it enters the digestive tract. The mantle (also known as pallium) is the dorsal epidermis in molluscs; all molluscs except some cephalopods are specialized to secrete a calcareous shell that protects the animal's soft body.