Many types of tea come from the same plant, Camellia Sinensis. The different types of tea (e.g. Black tea, Green tea, Pouchong tea, Oolong tea) are the result of differences in the tea manufacturing process.
One of the key steps in the tea manufacturing process, that is a factor in determining the type of tea, is the degree of fermentation the tea leaves are allowed to undergo. The term fermentation when applied to tea is something of a misnomer, as the term actually refers to how much a tea is allowed to undergo enzymatic oxidation by allowing the freshly picked tea leaves to dry. This enzymatic oxidation process may be stopped by either pan frying or steaming the leaves before they are completely dried out.