Pu Erh Tea is a completely different art. It first undergoes a process similar to Green tea, but before the leaf is dried, it's aged either as loose-leaf tea or pressed into dense cakes and decorative shapes. Pu Erh is a fermented tea (and the use of 'fermentation' is correct here, although not the type which produces alcohol).
Depending on the type being made (either dark "ripe" pu erh or green "raw" pu erh), the aging process lasts anywhere from a few months to several years.
Very old, well-stored pu erhs are considered "living teas", just like wine. They are prized for their earth, woodsy or musty aroma and rich, smooth taste.