Yoga is a Hindu spiritual and ascetic discipline, a part of which, including breath control, simple meditation, and the adoption of specific bodily postures, is widely practiced for health and relaxation.
Guided meditation is a state of relaxed concentration invoked and led by another party. The guide will instruct you to relax specific muscles in the body until they are comfortable, and will then lead you through mental images and visualizations, often of healing light or the dissipation of past wrongs. The purpose is to achieve mental, emotional and physical healing and stress relief.
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.