经络 The concept of channels (also commonly known as meridians) is fundamental to the system of Classical and Traditional Chinese medicine. The basics are easy to comprehend: there are pathways along which the vital energy (气 or Qi) flows. Disease, physical and mental, results when the flow is interrupted or unbalanced.
This concept is the basis of acupuncture, in which the needles are used at the source of the interruption (or a specifically effective point elsewhere) to return the qi to its normal course and so return the body to the balance of health.
Channels are also fundamental to Feng Shui, in which the arrangement (placement as well as the size, shape, and color) of items in a space will affect the qi and bring about changes in the energy of those who occupy the space.
In fact, even a brief list of Chinese systems and practices that involve qi would take up many pages, as it is so intrinsic to the overall Chinese way of thinking. Martial arts, meditation, philosophy…all of the various subgroups and interrelation of these disciplines depend upon an understanding of qi.
The most significant channels are called the “twelve standard meridians” and the “eight extraordinary meridians”. The twelve standard meridians are generally associated with specific organs, and are split between “hand” and “foot” channels. The eight extraordinary meridians are not associated with specific internal organs but are “vessels” that store qi (you could also refer to them as batteries).
There is no scientific proof of the existence of these channels, and tests and experiments conducted with Western scientific discipline have concluded that such things as acupuncture are not reliable (i.e., no better than a placebo). I am personally agnostic about channels; I hold out the possibility that the channels may indicate a deeper truth which Western science has yet to identify, and which Traditional Chinese Medicine recognizes but may possibly confuse with somewhat arbitrary traditional systems.
In any case there are a lot of people around the world who have been won over by the practice of these less than scientific methods. I could walk out o the street right now today & find person after person who have tried acupuncture & would swear to the effectiveness at healing the body. These people can not be convince that the practice is only a placebo & the real effect of the needles is not measurable. Still these people who have real relief every time they undergo the treatment tell their friends & family. They spread the word because of their experience with the healing touch not because of what science has told them is valid. These people have the ability to see that sometimes science does not know how to look to find what it wants to see.