Exfoliation is the removal of the dead, keratinized skin cells sitting on the skin's surface. Exfoliation leaves the skin smoother and fresher looking, and makes it easier for expensive facial products like serums to penetrate the skin's surface. It is an important part of both professional facials and body treatments.
However, exfoliation is a double-edged sword. It is easy to overdo facial exfoliation, especially, at home with overzealous scrubbing and cheap products like apricot kernel scrubs.
The skin on the rest of your body can take more vigorous exfoliation, more frequently.