Reiki is a Japanese technique for stress reduction and relaxation that also promotes healing. It is administered by "laying on hands" and is based on the idea that an unseen "life force energy" flows through us and is what causes us to be alive. If one's "life force energy" is low, then we are more likely to get sick or feel stress, and if it is high, we are more capable of being happy and healthy.
The wonder of Reiki is its simplicity - the real difference is in the Attunement (also known as Initiation) Process, where a Reiki Master reactivates chakras to enable the participant to channel (and vibrate) higher amount of Universal Life Force Energy.
Reiki is a spiritual, vibrational healing practice used to promote balance throughout the human system. Reiki does not involve physical manipulation or the ingestion or application of any substances, but works with the subtle vibrational field thought to surround and penetrate the body.