Reiki, originally developed and taught by Mikao Usui in Japan, is based on the concept of an universal life force, which flows in all living beings (and surrounds us as well known as the Self or the Divine or God or the one and only truth), and which we can access through prayer, attunements, alignment of our chakras, and then channel it onto others through our hands. The syllable "ki" means "life force", and it refers to nothing different but what is called "qi" or "chi" in other Asian, primarily the Chinese, traditions, the breath of God in the Christian teachings, and "prana" as known from yogic, and Ayurvedic philosophy.
Reiki is a simple and natural method of spiritual healing and self-improvement that everyone can use. It is administered by "laying on hands". Reiki energy work is safe for pregnant women, seniors, children, and even babies. From thousands of individual experiences it is known to reduce stress, promote relaxation, and harmonize imbalances. Reiki treats the whole person including body, emotions, mind and spirit. It is believed that a person’s “ki” or energy should be strong and free flowing. When this is true a person’s body and mind is in a positive state of health. When the energy becomes depleted or blocked it comes to symptoms of physical dis-ease or emotional imbalance. The Reiki practitioner can channel universal life energy into the patient, or more precisely be the channel through which the patient draws energy in, to activate the natural healing processes of the patient's body and restore harmony. For this reason Reiki works well combined with other medical or therapeutic methods to relieve side effects or promote recovery. Reiki works because it connects the universal life force energy with the body’s innate powers of healing.
While Reiki is spiritual in nature, it is not a religion. It has no dogma, and there is nothing you must believe in order to learn or use Reiki. In fact, Reiki is not dependent to belief at all and will work whether you believe it or not. The energy will always go where it is needed the most.