Tortoiseshell describes a coat, not a breed: black-based and orange-based colors mixed in patches or a fine blend, usually with little white. Add large white areas and the cat is called a calico. Dilute torties show soft gray and cream. Because the orange gene sits on the X chromosome, nearly all torties are female, and the rare males usually carry an extra X chromosome.
Most torties are domestic shorthairs, though the pattern also turns up in Persians, Maine Coons, British Shorthairs and many other breeds. The "tortitude" reputation for sass is mostly owner folklore, so a cat's age, history and socialization say far more than its color. Expect moderate shedding, which a weekly brushing handles, and a long commitment, since torties often live 12 to 18 years.