The practice of energy healing dates back at least 4,000 years. It is based on the idea that illness can result from imbalances in the "energy field" that surrounds and penetrates the human body. Consequently, health is restored by "re-balancing" this energy field.
If this sounds a bit "out there" keep in mind that acupuncture is based on an energy field flowing along meridian lines. And while it's a little less known, the chakra system is also based on an energy system.
Illness can also be the result of lowering body frequencies below the level necessary to maintain homeostasis. Health is regained by raising the frequencies and aligning the various bodies, so that all the fields come into alignment.
Some forms of energy therapy manipulate the biofields by applying pressure or manipulating the body by placing the hands through these fields. Examples include Qi Gong, Reiki, Emotion Free Therapy, and Therapeutic Touch.
When the individual's life energy (ie. energy field) is blocked because of trauma or stress, illness and suffering can occur. Using a holistic approach such as energy medicine, the natural flow of life energy can be unblocked to flow freely towards health and well-being again.
Note that energy healing is not intended to be the primary treatment for any health problem. It is a complementary therapy (and an excellent preventative measure) meant to support other ongoing physical, mental, and emotional treatments.