Microdermabrasion is a general term for products that have rough grains in them to help buff away the surface layer of skin. Although that sounds like it would be harsh - it's not really. There are many products and treatments that use this method both in home and in a clinic. Usually done on the face, chest, neck, arms and hands. What it does is help remove that epidermis level of skin - the dead skin cells on top of others that are in the process of maturing (that top layer is the Stratum Corneum). This is the layer that has minor imperfections in it. Microdermabrasion takes place at that level and remove dead skin, allowing the underlying newer skin to show thru. The crystals in the cream get rubbed against your skin so that they grab and remove dead cells. Look for products that do not contain a lot of fillers and find ones that contain nutrients and moisturizer so that while it's removing the dead cells, it's also hydrating the new skin in the same step.
It works great for cleaning out clogged pores and for those that might be too sensitive to Retin-A. There are conditions where it isn't suited like: Active rosacea, erythematosus, vascular lesions, widespread acne, herpes, warts, open sores, skin lesions, eczema, dermatitis, psoriasis, lupus, diabetes and those that take anti-coagulants or have fragile capillaries.