To assist the skin in its natural cycle of removing dead skin cells, an exfoliant or 'facial scrub' can be used - once or twice a week is sufficient for most skin. Some exfoliants are gentle enough to use more often, but beware of using scrubs too frequently, as they can often lead to irritation or worsen any current skin problems. Never use a body scrub, as it will be much too harsh on the delicate facial skin.
A facial mask will remove more toxins and impurities from your pores than a cleanser or exfoliant, and can be used to achieve a refreshed complexion, or encourage the removal of blackheads.
Some masks are wet, like mud, and need no preparation except for a clean face. Many natural clay masks however, come in their raw, dry form, and need to be mixed before application. Many products are multi-taskers and can be used either as a scrub, or a mask, with just a different approach to application.