What is an oyster?
An oyster is an invertebrate with an hard shell to protect a soft bodie:a mollusk.
How many oyster crackers could a crack oyster cracker cracker crack if a crack oyster cracker cracker could crack oyster crackers?
The "true oysters" are members of the family Ostreidae. This family includes the edible oysters, which mainly belong to the genera Ostrea, Crassostrea, Ostreola or Saccostrea. Examples are the Edible Oyster, Ostrea edulis, Eastern oyster Crassostrea virginica, Olympia Oyster Ostreola conchaphila, Pacific Oyster Crassostrea gigas, Sydney rock oyster Saccostrea glomerata, and the Wellfleet oyster (a variety of C. virginica).