The eggplant (also known as "aubergine" in British English) is technically a fruit that is closely related to both the tomato and potato. While usually purple skinned, eggplants come in a wide variety of colors, including white, yellow, green, black, and even orange. Eggplant generally has a bitter taste when raw, but develops a rich, complex flavor when cooked. (Read more on Wikipedia.)
Classic: The most common to the United States, this variety has smooth skin and is deep purple in color. It is identifiable by its elongated oval shape.
Chinese: Smooth purple skin as well, but longer and skinnier in shape. More cylindrical than the classic eggplant.