Shatter is a concentrate made by the cannabis plant that yields very high levels of THC, often 70-95%. CBD levels are much lower, and the result is often psychedelic with only a dose the size of a grain of rice.
It is extracted from the plant through a process that often uses a solvent (H2O, C2O, butane, alcohol, etc). The goal of concentrates is to eliminate all plant matter and extract the resin glands from the plant matter. The cannabis plant is mixed with a solvent then strained or purged to remove plant matter and any remaining solvents from the product.