Tea is processed by the following processes - oxidation, heating, drying and addition of leaves, buds, or twigs of the tea bush Camellia sinensis and other ingredients.
Four basic types of tea:
* white tea
* green tea
* oolong tea
* black tea

White tea -
It is made from young leaves that have undergone no oxidation. White tea is produced in lesser quantities than other types of tea and hence can expensive. It is mainly consumed in China.

Green tea -
Minimal amount of oxidation is used to produce green tea. Tea leaves may be left to dry as separate leaves or they may be rolled into small pellets to make gun powder tea. This process is time consuming and typically tea is processed within one to two days of harvesting.

Oolong tea -
Oxidation done is more than that of green tea. The whole oxidation process takes two to three days.

Black tea -
Black Tea is also known as red tea. The tea leaves are allowed to completely oxidize. The oxidation process takes between two weeks and one month.

Tea in India is produced in Assam, Darjeeling and Nilgiris. Tea type primarily produced
in India is black tea. Though Darjeeling also produces oolong tea and green tea.

Assam Tea is grown at sea level and is known for its body, briskness, malty flavor, and strong, bright color. Darjeeling tea has traditionally been prized above all other black teas, especially in the UK. When properly brewed it yields a thin-bodied, light-colored liquor with a floral aroma, a tinge of astringent tannic characteristics, and musky spiciness. darjeeling Tea leaves a sweet cooling aftertaste.

Major tea manufacturers in India are - Lipton Tea and Tata Tetley

Also see benefits of drinking tea.