There are two main types of Pu-erh. Sheng and Shu. Sheng is relativley unprocessed. The higher grades are usually pressed into disc shaped cakes and aged for years or even decades. The young puerh you mentioned probably refers to a loose form of sheng that was not pressed into cakes and not aged.
Shu puerh is made to mimic the taste of very old aged sheng. It is fermented or composted to accelerated the aging process. It is also pressed into cakes, bricks, and other shapes. The bird's nest mini tuocha is probably a shu puerh pressed into a shape resembling a bowl or bird's nest shape. The mini tuos are usually a single serving amount of tealeaves.
Puerh is a pretty broad subject and there is a lot of information here on TeaChat to learn from.