Despite the many names (bluepoint, Wellfleet, Kumamoto and Hamma Hamma), chances are you're choosing between two main oyster species: the Atlantic oyster, grown up and down the Eastern Seaboard, and the Pacific oyster. The European flat or Belon oyster and the Olympia oyster make up the two additional species grown in America. They are both harder to find.
Oysters take their names from the specific areas in which they grow. Because the water it inhabits greatly affects an oyster's taste, its origin is important. For example, a Wellfleet oyster tastes different from a Chatham oyster even though they both come from the waters off Massachusetts.
Oysters must be alive when you buy them, with shells tightly closed. They should be stored flat in the refrigerator to prevent their liquor from leaking out. Your fishmonger may be able to shuck oysters for you, but eat them as quickly as possible once they are out of the shell. You can also learn to shuck your own oysters.
Oysters taste delicious raw, stuffed or baked.
There is no substitute for an oyster, but hard-shell clams and mussels may be substituted in some recipes.