Acupuncture is a method of treating certain disorders by inserting needles into various parts of the body. It was developed in China about 2,000 years ago.
It works making use of "trigger points", which are areas of the body, usually in muscle, that are painful and cause the pain to radiate to other places, which may be some distance away from the trigger point. Inserting an acupuncture needle to the trigger point can relieve pain in these and the distant areas.
Acupuncture still works when there are no trigger points. This suggests that acupuncture acts by changing the ways in which the central nervous system (brain and spinal cord) is transmitting information about pain.
Acupuncture does have measurable effects on the body even though we can't explain them all in detail. You don't have to believe in it for it to work!
Interesting blog post
How acupuncture fits into osteopathy... click here