Tea is the agricultural product of the leaves, leaf buds, and internodes of the Camellia sinensis plant, prepared and cured by various methods. "Tea" also refers to the aromatic beverage prepared from the cured leaves by combination with hot or boiling water, and is the common name for the Camellia sinensis plant itself. After water, tea is the most widely consumed beverage in the world. It has a cooling, slightly bitter, astringent flavour which many enjoy.
There are at least six varieties of tea: white, yellow, green, oolong, black, and pu-erh of which the most commonly found on the market are white, green, oolong, and black. All teas are made from the same species of plant, though different varieties may be used, and the leaves are processed differently, and, in the case of fine white tea, grown differently. Pu-erh tea, a post-fermented tea, is also often used medicinally.
The term "herbal tea" usually refers to an infusion or tisane of leaves, flowers, fruit, herbs, or other plant material that contains no Camellia sinensis. The term "red tea" refers to an infusion made from either black tea (mainly in Chinese, Korean, Japanese and other East Asian languages) or the South African rooibos plant (containing no Camellia sinensis).
According to Mondal (2007, p. 519): "Camellia sinensis originated in southeast Asia, specifically around the intersection of latitude 29°N and longitude 98°E, the point of confluence of the lands of northeast India, north Burma, southwest China and Tibet. The plant was introduced to more than 52 countries, from this ‘centre of origin’."
Based on morphological differences between the Assamese and Chinese varieties, botanists have long asserted a dual botanical origin for tea; however, statistical cluster analysis, the same chromosome number (2n=30), easy hybridization, and various types of intermediate hybrids and spontaneous polyploids all appear to demonstrate a single place of origin for Camellia sinensis — the area including the northern part of Burma, and Yunnan and Sichuan provinces of China. According to this theory, tea plants in southeast Asia may have been the products of the 19th Century and 20th Century hybridizing experiments.
Yunnan Province has also been identified as "the birthplace of tea the first area where humans figured out that eating tea leaves or brewing a cup could be pleasant." Fengqing County in the Lincang City Prefecture of Yunnan Province in China is said to be home to the world's oldest cultivated tea tree, some 3,200 years old.