What Is A Clam?

They are considered a bivalve mollusk, and are a muscle that resides in salt water and sand. There are many different types of clams, and they all have different flavors. Here are some of the names of them.
Ark clams, nut clams, duck, marsh, file, hard, soft, surf, ocean quahog, Pacific razor, giant, asian or asiatic, peppery furrow shell, and pismo. Hope this helps, good luck.

Common name frequently used to refer to certain freshwater bivalves (ie, fingernail clams and the Asiatic clam).

One of many varieties of mollusks en.wikipedia.org

A clam is a bivalve mollusk that burrows under the bed of the freshwater or ocean environment that it lives in.  They belong to the class Pelecypoda, and there are several different animals that are considered to be clams.  All clams have a symmetrical hinged shell that houses and protects them from the elements and predators.  Some clams will attach themselves to rocks in shallow areas.  

Clams are a popular meal for humans living in coastal regions.  Clams are available to buy fresh from fish markets and are also preserved and shipped around the world.  Burrowing clams are quite easy to harvest and many people who live on the coast are familiar with clam digging.  Clams that have attached themselves to rocks need only be pried away gently.  Clams eat plankton and are themselves eaten by a number of oceanic mammals and fish.  

Clams are classified as having a roughly oval shape, reproducing sexually, and having a simple open circulatory system.  Although they do not have eyes or a brain, clams do have a heart and kidneys.  There are two divisions for clams: Hard shell and soft shell.  Some examples of soft shell clams include geoducks, razors, and steamers.  ‘Soft shell clam’ is a misleading name because these clams have brittle and thin shells, rather than soft.  Soft shell clams often cannot retract their necks all the way which means that a portion of the clam will protrude outside the shell at all times.  Hard shell clams can retract their bodies entirely into their shell and have a more typical, solid shell.  Common hard shell clams include chowders, butters, and littlenecks.

People who live near the water and participate in clam digging should be familiar with red tide.  Clams and other shellfish can accumulate biotoxins and should never be harvested during red tide warnings.  It is common for coastal regions to have a hotline people can dial to get up-to-date information about whether shellfish are safe to harvest for consumption.  Shellfish can also deteriorate very quickly so clams should always be cooked while they are alive.  Dead clams should be discarded.  To test whether a clam is alive is quite easy.  For hard shell clams, their shell will be tightly closed if they are alive.  If the shell is open, tap it gently.  If the clam is alive, it will snap its shell shut.  With soft shell clams, touch their neck to see if they retract.  If they do not, they are dead and should not be eaten.

A clam is an animal that resides in the sea.