Most people seem to shy away from the world of Puerh, but Puerh tea is a unique and innovative category of tea. The depth of Puerh lies in the post-processing fermentation it goes through. This refers to the chemical process of fermentation the tea leaves undergo after they are done with the standard processing steps. All Puerh teas will be fermented to a different degree, so no two Puerhs will ever be exactly the same!
Fermentation can be induced in a variety of ways that end up determining the subcategory the tea falls into; ripe and raw. Don't let the intricate process intimidate you, it not only determines the subcategory, but it's also what makes the flavor so complex and unique.
Puerh is post- fermented tea.
Raw Puerh: Raw puerh tea is the original method of making puerh that was invented hundreds of years ago. Tea leaves are compressed into various shapes or left loose, then just left to age. Raw puerh tea takes up to 30 years to become "fully fermented". This means all raw puerh tea is on its way to becoming "fully fermented" and therefore the difference between various ages of raw puerh tea be much more obvious than ripe puerh tea.
Ripe Puerh: Ripe puerh tea is a very new phenomenon, only having been invented in 1975. It was originally invented to accelerate the lengthy aging process of raw puerh tea to satisfy the growing demand. Ripe puerh tea is "artificially" fermented in a loose form. Ripe puerh tea is a made by "piling" tea leaves. "Piling" is the process of gathering tons, literally tons, of tea leaves and first making them into large piles in a temperature controlled environment. Then the tea leaves are sprinkled with water and covered with large cloths. The artisans will periodically stir the tea leaves and sprinkle more water on to control the fermenting process. The tea leaves will become "fully fermented" within a period of about a month.