Pu-erh or Pu'er tea (pǔ'ěr chá) is a variety of fermented dark tea produced in Yunnan province, China. Fermentation is a tea production style in which the tea leaves undergo microbial fermentation and oxidation after they are dried and rolled. This process is a Chinese specialty and produces tea known as Hei Cha, commonly translated as dark, or black tea. 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.
Pu'er traditionally begins as a raw product known as "rough" Mao Cha and can be sold in this form or pressed into a number of shapes and sold as "raw" Sheng Cha Both of these forms then undergo the complex process of gradual fermentation and maturation with time. In the mid-1970s Tea Factories created a new type of pu-erh tea, with a process that involves an accelerated fermentation into "ripe" Shou Cha which is then stored loose or pressed into various shapes. All types of pu-erh can be stored to mature before consumption, which is why it is commonly labelled with year and region of production.