For your edification:
Pu-erh is aged tea that is withered, rolled, and allowed to re-ferment in warm, humid conditions before being dried or pressed into cakes, dumplings, or any other amazingly adorable shapes. Some Pu-erh teas can be drunk right after processing (shu) while others are meant to age after production (sheng), like fine wine, and some even are aged for hundreds of years and can become a valuable commodity, and often a symbol of status.
This processing style, and the secondary fermentation originate in China in the 7th century or so. Trade routes were long and wet and horses were sparse. The tea would moisten in the rain and begin to ferment on their six to eight month travels, which mellowed the vegetal green teas into something more fruity, earthy, and smooth.
Pu-erh has been a staple in Chinese medicine for two thousand years and is reputed to have phenomenal health benefits, for instance, drinking pu-erh has been shown to reduce toxins in the blood and lower cholesterol by stimulating the activity of the spleen and stomach and increasing blood circulation. It also helps aid in digestion after a large meal, and get you off your buns with a little caffeine jolt.