There are a lot of stories and claims about how tea was invented, but the oldest writing is Chinese. In 2737 BC emperor Shen Nung , also known as the "Divine Healer", unwillingly discovered the treat of brewed hot tea.
Tea; Camellia sinensis a warm weather evergreen plant, that grows into 30 feet or more in the wild, and under such a tree the Divine Healer was one day seated for his meal. One of the things he was noted for was to boil any drinking water before use, a wise thing even today, and so some leaves from a nearby tree fell into the water pot and produced a fragrent and well tasting brew, and so tells the legend, Tea was invented.
Tea bushes as we know them today are the very same plant, but they are now pruned to be about 3 feet high. The leaves are hand-picked and processed into what we know as tea. There are 3 types of tea; Green, Oolong and Black (also referred to as "Red") tea. What differs them are the level of process they go through; green tea goes through the least and black the most.
Tea goes through these processes: Following picking, tea is whitered, rolled, oxidized, fired, graded and packed.
A fourth type of tea, called White Tea, is the buds of the tea plant. It produces a very mild and gentle brew. White Tea is very expensive and exclusive.
Then we have the Herbal teas, that are not really teas at all. Herbal teas are not from the Camellia sinesis plant, but from various plants and herbs and include leaves, flowers, stems and roots. These are often referred to as Herbal Teas or Tisanes.