PAD is a condition in which arteries, the blood vessels that deliver oxygen and nutrients to all the cells of our body, become clogged or otherwise blocked.  The word peripheral describes the part of the circulatory system away from the heart and brain.  For the foot, it specifically describes disease of arteries in the legs.  In fact, when people are discussing PAD, it is usually referring to leg circulation, as opposed to the arms.  Arteries can develop areas or plaque, or wall blockages, that can restrict flow down the legs further past the blockage.  The process is similar to the one that causes blockages in the heart arteries that lead to heart attacks.  When the leg blockage occurs with enough severity, the tissues in the foot affected will slowly starve, lacking vital oxygen and nutrients.  This can result in tissue damage, wounds, severe pain, gangrene, and even amputation.