Pu-erh or Pu'er is a variety of fermented and aged dark tea produced in Yunnan province, China. Fermentation in the context of tea production involves microbial fermentation and oxidation of the tea leaves, after they have been dried and rolled. This process is a Chinese specialty and produces tea known as Hei Cha (黑茶), commonly translated as dark, or black tea (this type of tea is different from what in the West is known as "black tea", which in China is called "red tea" 红茶). The best known variety of this category of tea is Pu-erh from Yunnan Province, named after the trading post for dark tea during imperial China.