Oolong Tea is a category of tea that includes a broad range of tea types. You can generally divide Tea into three main categories: Green, Oolong, and Black. The level of oxidation of the tea is what determines these three categories. Green Tea is unoxidized, Oolong Tea is partially oxidized, and Black Tea is fully oxidized. Almost all tea is made from the leaves of the tea plant Camellia sinensis, though there may be variations in specific variety of plant used.