In traditional Chinese medicine (TCM) the body is seen as a delicate balance of two opposing and inseparable forces: the yin and yang concept of two opposing yet complementary forces described in traditional Chinese medicine. Yin represents cold, slow, or passive aspects of the person, while yang represents hot, excited, or active aspects.*
A major theory is that health is achieved through balancing yin and yang and disease is caused by an imbalance leading to a blockage in the flow of qi. Yin represents the cold, slow, or passive principle, while yang represents the hot, excited, or active principle.*
According to TCM, health is achieved by maintaining the body in a "balanced state"; disease is due to an internal imbalance of yin and yang. This imbalance leads to blockage in the flow of qi. In traditional Chinese medicine, the vital energy or life force proposed to regulate a person's spiritual, emotional, mental, and physical health and to be influenced by the opposing forces of yin and yang. (vital energy) along pathways known as meridians. Qi can be unblocked, according to TCM, by using acupuncture at certain points on the body that connect with these meridians.*
Sources vary on the number of meridians, with numbers ranging from 14 to 20. One commonly cited source describes meridians as 14 main channels "connecting the body in a web like interconnecting matrix" of at least 2,000 acupuncture points.*
Source: http://nccam.nih.gov/health
