According to NCCAM, CAM is defined as "a group of diverse medical and health care systems, practices, and products that are not presently considered to be part of conventional medicine." 
"complementary" medicine is used together with conventional medicine, whereas "alternative" medicine is used in place of conventional medicine.
It was classified into four categories or "domains." These are:
1. Biologically-based practices
"biologically based practices" include botanicals, animal-derived extracts, vitamins, minerals, fatty acids, amino acids, proteins, prebiotics5 and probiotics,6 whole diets, and "functional foods".
Many biologically-based products within this class are subject to statutory and regulatory requirements under the Act or the PHS Act. The intended use of a product plays a vital role in how it is regulated. For example, these Botanical products, according to conditions and circumstances, may be used as drugs, cosmetics, dietary supplements, or foods. Furthermore, a botanical product intended for use in treating a disease would generally be regulated as a drug; a botanical product taken by mouth, labeled as a dietary supplement, and intended for use to affect the structure or function of the body would generally be regulated as a dietary supplement. 
2. Energy therapies
It involves energy fields of two types:
- Veritable energy fields, which can be measured and use either mechanical vibrations (such as sound) or electromagnetic forces, including visible light, magnetism, monochromatic radiation (such as laser light), and other light rays.
- Putative energy fields (or biofields) that have defied measurement to date by reproducible methods.
CAM products use veritable energy fields in the diagnosis of disease or other conditions or in the cure, mitigation, treatment, or prevention of disease in man or animals or to affect the structure or any function of the body of man or animals may be medical devices under the Act. 
As well, CAM products use putative energy fields in the diagnosis of disease or other conditions, or in the cure, mitigation, treatment, or prevention of disease in man or animals may be medical devices under the Act. For example, acupuncture needles as "class II" medical devices. 
3. Manipulative and body-based methods:
According to NCCAM: It includes chiropractic and osteopathic manipulation, massage therapy, Tui Na, reflexology, rolfing, Brown technique, Trager bodywork, Alexander technique, Feldenkrais method, and a host of others..
Manipulative and body-based practices focus on the structures and systems of the body, including the bones and joints, the soft tissues, and the circulatory and lymphatic systems. 
4. Mind-body medicine.
Mind-body medicine is defined as "the interactions among the brain, mind, body, and behavior, and the powerful ways in which emotional, mental, social, spiritual, and behavioral factors can directly affect health."13 It states that mind-body medicine "typically focuses on intervention strategies that are thought to promote health, such as relaxation, hypnosis, visual imagery, meditation, yoga, biofeedback, tai chi, qi gong, cognitive-behavioral therapies, group support, autogenic training, and spirituality." 
How Do CAM Relate to Products That FDA Regulate?
FDA intends to
Detect which CAM classes should be subject to regulation under the Act.
Show that neither the Act nor the PHS Act contains any exemption for CAM products.
- See NCCAM, "Get the FACTS - What Is Complementary and Alternative Medicine (CAM)?" available at http://nccam.nih.gov/health/whatiscam (accessed on November 22, 2005).
- "BACKGROUNDER: Biologically Based Practices: An Overview" (October 2004), at page 1 (available at http://nccam.nih.gov/health/backgrounds/biobasedprac.pdf) (accessed on November 22, 2005))
- U.S. Food and Drug Administration. 2021. Guidance on Complementary and Alternative Medicine Products. [online] Available at: <https://www.fda.gov/regulatory-information/search-fda-guidance-documents/complementary-and-alternative-medicine-products-and-their-regulation-food-and-drug-administration> [Accessed 9 April 2021].
- BACKGROUNDER: Manipulative and Body-Based Practices: An Overview" (December 2004), at page 1 (available at http://nccam.nih.gov/health/backgrounds/manipulative.pdf) (accessed on November 22, 2005).