Acupuncture is one of the branches of Traditional Chinese Medicine.  In the body there is a universal life energy called Qi (pronounced chee) which flows throughout the body in channels that are called meridians and is accessed by inserting needles into specific acupuncture points.  The needles used are sterile and very small, about as thick as a human hair.  They cause little discomfort upon insertion and some people do not feel anything while others may feel a slight pinch.  When the qi of the body is reached by shallow insertion people may feel a slight ache or a tingling sensation.