Pu-erh is fully oxidized like a black tea, and then fermented. It was traditionally pressed into cakes for transportation, but we have it loose as well. It is one of the oldest type of tea in China with a rich history of over 1700 years that can be traced back to the Eastern Han Dynasty (25-220 AD).
Pu-erh should be “rinsed” once with hot water (steep for about 5-10 seconds and discard the water), and then can be brewed over and over. It will still produce a good cup of tea the 6th or 7th time you use the leaves. Pu-erh has lots of caffeine, especially in the first infusion.
“Raw” pu-erh is similar to an earthy green tea, and has not gone through the full aging process that the “ripe” pu-erh goes through. Ripe pu-erhs are often used to aid digestion and weight loss.