Black tea, or red tea as it's known in China, is made from fully oxidized leaves. To make black tea, the leaf is spread out and left to wither naturally, causing it to lose stiffness and much of its weight. It is then rolled, exposing essential oils to the air and encouraging oxidation. When this is complete, the leaf is heated to stop the process. These teas tend to be full-flavored and can stand up to milk and sweetener.
Major regions of production include India, China and Sri Lanka, although this type is grown throughout the world. It was popularized by European merchants that traded in Asia in the early 1800s, which contributed to its current dominance in the West via strong breakfast teas.