Tea Bricks are blocks of whole or finely ground tea leaves that have been packed and pressed into molds. Developed in Ancient China, it made tea easily portable and took up little space when traveling the trade routes. One would simply "shave" off the amount of tea needed, then either toast it over a fire or grind the leaves down into a powder before infusing with hot water.
Today, teas such as pu-erh (above) are commonly found in bricks, discs, and other pressed forms, and many tea companies sell Tea Bricks for use as a decorative object or teaching tool.
I have a Tea Brick and it's a great conversation starter!