Some consumers incorrectly think that these terms refer to types of tea leaves, but they simply refer to the process . At the other end of the spectrum are green teas . These are steamed and rolled, same as black, but are then immediately fired to prevent aging and fermentation. Incidentally, both black and green teas get their names from the appearance of the processed leaves, not from the color of the liquor. Green tea is the drinker's choice in Japan, which is also the world's largest producer of this type.
Some oolong is produced in China, but it's generally considered inferior to the Formosan.
Black tea is graded by size. Smaller leaves and broken leaves will produce a stronger brew for the same brewing time and water temperature, and are thus popular in blends. But in fact, these graduations tell you little about the quality of black tea itself. Since many teas are ground or cut before being placed in bags, these classifications aren't very useful to the consumer. But again, this is no direct indication of quality.