The term ‘alternative medicine’ encompasses any healing practice "that does not fall within the realm of conventional medicine." Most common practices are  homeopathy, naturopathy, acupuncture, chiropractic, midwifery and herbal medicine.

Alternative medicine is also known as complementary medicine/therapy. More often the umbrella term Complementary and alternative medicine (CAM) is used.

Alternative medicine practices may incorporate spiritual, metaphysical, or religious underpinnings, pre-modern medical traditions, or newly invented approaches to healing. They may be based on traditional belief systems, folk knowledge, or more recent ideas, but by definition are not based in the standards of conventional medicine. Often, the claims made by alternative medicine practitioners are not based on rigorous scientific investigation. However, if scientific investigation shows that an alternative medical approach is safe and effective, it may be adopted by conventional practitioners. Even if there is no evidence showing efficacy, many alternative practices are often licensed and regulated in ways similar to conventional medical practices.

However many books, schools and universities separate all the therapies into four distinct categories and they are -  

Alternative Medicine
Alternative medicine is any form of practice that is outside the realm of conventional modern medicine. It covers a broad range of healing philosophies, approaches, and therapies. Most of these treatments and health care practices are not taught widely in medical schools. Examples are osteopathy, naturopathy, chiropractic, ayurveda, homeopathy and acupuncture.

Complementary Medicine
If alternative medicine or therapy is used alone or instead of conventional medicine, it is called "alternative" medicine. If the treatment or therapy is done along with or in addition to conventional medicine, it is referred to as "Complementary Medicine" as the two practices complements each other. For example, many Chinese hospitals use acupuncture to reduce the pain during the surgery instead of anesthetics. This is complementary medicine.

Holistic Medicine
Many of the alternative practices pay attention to the mental, emotional, and spiritual aspects of health, in addition to the physical body. Therapies like hypnosis and visualization claims to be able to change physical conditions through purely mental interventions. They believe that our bodies are remarkably resilient machines, capable, with some occasional prodding or intervention, of healing themselves. The name "holistic medicine" came from this unification of the mind and the body. Holistic practitioners treat the "whole person" as opposed to the individual organs of the body where symptoms occur. The importance of self care and preventing illness are stressed by holistic practitioners.

Natural Medicine
Any therapy that relies on the body's own healing powers may be considered natural medicine. These include herbal remedies, diet and water therapies.