By Jeffrey Singer, an excerpt from "Acupuncture, A Brief Introduction"

Cupping is another type of treatment. This is a method of stimulating acupuncture points by applying suction through a metal, wood or glass jar, in which a partial vacuum has been created. This technique produces blood congestion at the site, and therefore stimulates it. Cupping is used for low backache, sprains, soft tissue injuries, and helping relieve fluid from the lungs in chronic bronchitis.