The clam shown at the left was saved from being eaten with bread crumbs and oregano. Its reward in life is that YOU get to learn something from it. Make its sacrifice a noble one and observe a few things. The shell is hardened calcium. There aren't too many things that can crack it. Its great protection. Also notice the large structure at the bottom of the picture called the foot. It acts, quite obviously, as a foot. Clams move with this structure. Not very well, but they do.

Clams are filter-feeders. This means they suck in water, filter out and eat whatever nutritious food (algae/plankton) happens to be living in the water and spit the water right back out.