The word Reiki is made of two Japanese words - Rei which means "God's Wisdom or the Higher Power" and Ki which is "life force energy". So Reiki is actually "spiritually guided life force energy." 

Reiki is a very specific form of energy healing, in which hands are placed just off the body or lightly touching the body, as in “laying on of hands.” Reiki can also be done “long-distance,” as a form of prayer. According to many versions of its origin, Dr Mikao Usui, a Japanese seeker of spiritual truths, brought the Reiki method of healing into human awareness in 1922 after a deep spiritual experience. 

In a Reiki session, the practitioner is seeking to transmit Universal Life Energy to the client. The intention is to create deep relaxation, to help speed healing, reduce pain, and decrease other symptoms one may be experiencing.