Reiki (pronounced ray-key) is a laying-on of hands energy healing technique. Based on ancient wisdom it was developed in Japan by a Buddhist monk named Usui Sensei in the late 1700s and early 1800s. It has been described as a form of Shinto/Buddhist Qigong. Besides the potential of healing the body, as a Buddhist practice it can be used to lead one to transcend the ego and see "Reality".
Usui Sensei founded a group in Japan (the Usui Shiki Ryoho in Tokyo) to continue on with the practice after his death. Since his death in 1826 there have been five "presidents" or successors. The current successor is Ms. Kimiko Koyama. Although Reiki has been in practice in Japan since Usui's death, it wasn't until 1980 that it was popularized in America and other Western countries. It is very sad how in the West the Buddhist practice of Reiki has been so commercialized, mixed with so much disinformation, used for ego building, and made very "wu-wu". Transcending the ego is something Westerners (myself included) generally have a very hard time with.