Healing is the transmission of psychic energy for therapeutic purposes. It is practiced throughout the world in countless ways, ranging from conventional prayer to outrageous quackery.
Faith healing, to activate the patient's own self-healing abilities, works by the power of suggestion or by hypnosis and requires the patient's belief in the healer. Spiritual or psychic healing involves the transmission of some form of energy from the healer to the patient and does not depend on the patient's belief.
The healer may be a religious person, attributing his powers to God; others attribute the source of the energy to discarnate entities or departed spirits, or the fact that they themselves are able to focus natural forces.
A systematic review of randomized and controlled trials of distant healing found that about half of the studies suggested it was effective, although methodological shortcomings prevent any firm conclusions. Many patients with advanced cancer seek healing. Rare dramatic responses have been reported but are difficult to substantiate.

Woodruff R. Palliative medicine evidence-based symptomatic and supportive care for patients with advanced cancer. 4th ed. Oxford University Press, 2004. p. 491.