According to legend, in 2737 BC, Chinese Emperor Shen Nung was boiling drinking water over an open fire and a few leaves from the Camellia Sinensis plant fell into the pot of water. He drank the mixture, and being known as the Devine Healer, declared that it gave one "vigor of body and contentment of mind."
Tea drinking became a popular social custom for China's elite. But it took until 1640 for tea to make it Europe and until 1670 to sail to the Americas. Then tea really took off!
At the World's Fair in St. Louis in 1904, Thomas Blechynden was trying to sell his hot tea, but because of the hot weather, no one was buying, so he added ice, and VOILA! Southerners have to thank this man, because today iced tea is considered the "table wine of the South."
So, all tea comes from the same plant, a first cousin to the Southern camellia bush--Camellia Senensis (a warm-weather evergreen). It is the region it was grown, the time of year picked, stages of processing, and contact with oxygen that determines the types of tea that end up in your teacup.

It's important to know that all tea comes from the Camellia Senensis plant and contains caffeine, but less than half the amount of caffeine as coffee. Tea may be partially decaffeinated, but it will still contain caffeine.
So now you have a brief of history of tea and how it is processed.