Black tea is tea that has been fully oxidized (sometimes referred to as being "fermented" although it is not a true fermentation process). Both the leaves and brewed tea tend to have a dark color, although some black teas are golden or greenish in color. In Chinese, black tea is called hóngchá(紅茶), meaning red tea, although in English, red tea more often refers to rooibos, an herbal tea that is not made from the tea plant.
Black tea also tends to contain more tannis, chemicals giving the tea its characteristic dark color. The tannins are actually a form of antioxidants, and are the chemicals that the catechins of green tea are transformed to when they undergo oxidation.
