Reiki (霊気) (/ˈreɪkiː/) is a form of alternative medicine developed in 1922 by Mikao Usui. Since originating in Japan, reiki has been adapted into varying cultural traditions across the world. Reiki practitioners use a technique called palm healing or hands-on healing through which a "universal energy" is supposedly transferred through the palms of the practitioner to the patient in order to encourage emotional or physical healing.
Reiki was founded by a Japanese Buddhist monk named Mikao Usui (臼井甕男, 15 August 1865 – 9 March 1926) in 1922.[Many proponents hold that he rediscovered Reiki as part of his search of "sacred texts," but it’s basically a rehash of similar practices such as pranic healing, Qi Gong, therapeutic touch and other hand-waving or laying-on-of-hands therapies that make the patient feel they’re getting paid attention by someone. Today it is considered to be a form of alternative medicine. It is generally considered to be "not a religion" by its adherents, even though some adherents claim that it has Buddhist origins.
From its invention in Japan in 1922, Reiki has split into many schisms (similar to the process whereby religions split into denominations). Like religious denominations, there are far too many to list here, but a few of them include: Usui Reiki (the original); Western Reiki, brought to Hawaii by Hawayo Takata, which most Western varieties spring from; Gendai (Modern) Reiki, an updated Japanese version; Rainbow Reiki, which combines Reiki with chakras; Five Element Seichem, a recent variant from Canada; Kundalini Reiki, another version crossed with chakras, which appears particularly suited to distance learning; The Radiance Technique, which has chakras, seven levels, and was apparently discovered by aliens; and, of course, tantric Reiki, which is just what it sounds like. But very spiritual.