Beardruff is a misnomer, meant to signify flaking from the facial skin similar to how dandruff is flaking from the scalp. Beardruff is not the same thing as dandruff on the scalp. Rather, it's the same thing as dry scalp, a different condition than dandruff.

Nevertheless, whenever you hear the term beardruff, remember that it simply means dry, flaky skin underneath one's beard.