It is administered by "laying on hands"  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.  

Reiki as a healing art was first developed in Japan.  When interpreting the word reiki, there are many factors to consider.  Since the Japanese language is so subtle, each word or syllable carries  multiple layers of meaning. Therefore, there are many slight variations  on the way in which it can be defined; and yet, a common thread runs  through them all.  

Reiki is actually composed of two Japanese characters (or kanji): rei and ki. We like to define them in this way:  

Rei represents the energy of Source or Higher Consciousness, and incorporates the mystery of the unknown.  

Ki  represents the energy of Life. It is also called chi in Chinese, prana  in Sanskrit, manna in Hawaiian, and life force in English. When  combined to form the word Reiki, these two kanji represent the energy of  Universal Life, the harmonization of body and soul.