Compressed tea, also known as tea cakes or tea bricks, are tea leaves that are steamed and then pressed into a round shape (or other desired shapes). This method was applied in ancient China for a few reasons: tea cakes were more compact than loose tea and also less susceptible to physical damage during transport over land on the ancient Tea Road. In smaller forms, pressed tea cakes were also used as a means of payment. Some high-quality teas age like a good wine, and the best way to age tea, especially Pu Erh tea, is by pressing it.
To make the infusion, take small amounts of compressed leaves using a knife or awl directly from the cake and then let them steep in the usual way.