There can be some really interesting discussions among professionals about each of these, depending on the perspective of the person talking. Each of these can take take you to an alternative state of awareness where a lot of beneficial effects can occur. In this altered state of awareness healing can occur. Your body can rejuvenate itself. I began with Vipasana meditation, which is a classical meditation technique focusing on the inhalation and exhalation of the breath regardless of the distractions from the mind or body. When I began studying Tibetan Buddhism my teacher discouraged that form of mediation for mantras and recitation of set practices. At times I still use both of these approaches. Frequently I use Eckhart Toole’s focusing on the light within the body. Guided imagery usually involves someone else guiding you to a scene or image or feeling. Sometimes the student can use that scene or image to focus on for mediation at a later time. Guided imagery is similar to hypnosis although often there is not a formal induction with guided imagery. One teacher I studied with was very opposed to hypnosis but used guided imagery frequently. From my perspective it was very much like hypnosis.