Black tea is known literally as red tea in China. The tea leaves are rolled until completely bruised, thereby breaking open the cells and allowing total oxidization. It is this process which causes it to have the highest caffeine content.
Black tea is the main tea familiar to people from across Europe and North America. However, its origins are from China. Legend has it that the Emperor only allowed trade of the unwanted varieties of Chinese tea, though its early export is more likely due to the black tea being better suited for long distance transport. Black tea in China is not consumed as often as other varieties, though those which are popular stand out with unusually delicious tastes and dark, complex aromas.