Acupuncture is use of serile single use needles (.25 -.3 mm wide) into the body at specific points for a desired theraputic effect. Acupuncture has been proven by the world health organization (WHO) to be an effective treatment for dozen of conditions.
traditionally and currently it is used to treat a wide range of conditions in all systems of the body. (Reproductive, digestive, hormonal, emotional, dermatological, musculoskeletal, neurologic, circulatory, and respiratory)
People are always curious if it will hurt. Acupuncture should be a painless experience, sometimes a slight pinching sensation can be felt for a slip second as the needle is being inserted.
Here is a helpful reference picture.