Pu-erh (or Pu'er tea) is a fermented tea, named after Pu'er county near Simao, Yunnan, China. It is an unusual tea, because unlike other teas which are consumed shortly after production, it is often aged before consumption; it is not impossible to find pu-erh older than 20, 30, or even 50 years. Indeed, connoisseurs pay heavy prices for older pu-erh, and classify the teas by year of production, much like a wine vintage. In addition to loose leaf, pu-erh tea is typically bought in cakes of compacted tea (see Tea brick).

Unlike other varieties of tea, pu-erh is traditionally made with leaves from tall, old trees. These trees are of a varietal known as "broad leaf tea" (´óÒ¶, d¨¤ y¨¨) found only in southwest China and bordering regions in Burma, Vietnam, and Laos. The leaves are covered with fine hairs, are larger than other tea leaves, and have a different chemical composition. Leaves from old tea trees growing in the wild on different "tea mountains" are highly valued; more and more, connoisseurs seek pu-erh with leaves taken from a single tea mountain's wild forests, unblended with leaves from any other areas.

Oftentimes pu-erh leaves are formed into cakes or bricks, wrapped in paper or pomelo rinds, and stored away from excessive moisture, heat, and sunlight in order to further mature. After being stored for many years, the tea takes on darker, mellower characteristics that come with age. This feature of pu-erh probably originated from the natural aging process that happened along the ancient caravan routes[1]. The tea bricks developed a unique clean earthy flavor that was then refined by aficionados.