Shapton Lapping Powder is meant to help you lap your (Shapton) sharpening stones. The bottle is filled with coarse silicon carbide grains. You use these grains in combination with, for instance, the Shapton Naoru Lapping System or a glass lapping plate.
The coarse lapping powder is used to lap sharpening stones with a grain size ranging from 120 to 1.000. If you are planning to lap a sharpening stone with grain size 1000, use the medium lapping powder. Properly clean the lapping plate after use to make sure you grains are left behind.