Reiki is a universal healing source that was discovered by Dr. Mikao Usui in the early 1900''s. Dr. Usui was at a low point in his life, enduring financial and physical hardships. He went to a Buddhist Monastery for a retreat. On this retreat, he adhered to a sixty-day regimen of fasting, prayer, and intense desire to find his way out of his hardships. He was looking for spiritual guidance. It could not be found. On the last day, under a holy waterfall, enlightenment hit. He was filled with energy from the spirit. He dedicated his life to the sharing of this beautiful energy for the benefit of mankind.
One of his students, Mrs. Hawayo Takata, came to him after a stunning revelation on the operating table. She was scheduled for cholecytectomy (open gallbladder removal). She realized it did not have to be this way, cancelled the operation, and began a series of treatments with Dr. Usui. These healings were a 'laying on of hands' using this healing source. In some time, all of her symptoms relented. She was in good health and pain free. She asked Dr. Usui to teach her. She is the student that brought Reiki to the west.
Rei = Spiritual Wisdom Ki = Life Energy
For more on the history of Reiki, a good book is 'Reiki The Healing Touch' by Dr. William Rand.