Distant healing (aka absent healing), basically means sending the reiki energy through time and space.  The whole universe is energy, and even though everything appears to be solid and of substance, when you break everything down, it is basically pure energy.  The planet is energy, the wind and ocean is energy, and even ourselves and our thoughts are just energy.  It's just that this energy comes in different forms, which can change through time.  And on this fact, comes the understanding that reiki energy can be sent through time and space.  Reiki energy is universal life force energy.  This is the energy which surrounds and connects all things.  Most reiki practitioners use distant healing to send the energy to people or situations.  The people may be on the other side of the planet.  Whatever the distance, it does not make any difference.  As long as the intent is there, and the symbols are used, the practitioner and the recipient will connect.  The recipient can often feel subtle sensations during the distant healing session.