They are composed of either particles or physical abraders such as sandpaper, steel wool, scrubbing pads, etc. The finer the particle the less are less abrasive and the coarser the particle the more abrasive. Baking soda and salt can be used as abrasives. Baking soda is finer, less abrasive. Salt more abrasive.
Abrasives dull glossy surfaces and change both the reflection from, and texture of, surfaces.
They should never be used on mica because they take away top layers making future cleaning eventually impossible. Mild Abrasives include fine plastic mesh pads, nylon coated sponges, fine brass wool, rotten-stone and whiting. Mild abrasives are used to scour pots and pans, oven interiors, and drip pans. Use as directed to remove stains on surfaces as furniture, countertops, etc. Abrasives will scratch fine, hard, smooth surfaces if you rub hard.