It is a mixture of fine abrasive powder used in marble floors, terrazzo or granzon formulated to remove marks or stains deeply penetrated that are not removable with normal polishing before polishing.
It can be manufactured in different abrasive grains, from thin one to thick one, depending on the size of the scratch or stain.
Use a floor polishing machine with a brush at low speed, you can also use disk-type abrasive fibers for its application.