Acupressure is the art of pressing on certain spots on the human body (yourself or a willing recipient) in order to produce certain therapeutic and/or relaxing effects. Usually proper acupressure requires at least a little sensitivity by the practitioner, a hand or two, and approximately three to ten minutes of pressing in the location(s) recommended. This procedure helps centers of "chi" to balance themselves, thus resulting in improved physical and even mental conditions. Acupressure is considered part of Traditional Chinese Medicine, and is very closely related to acupuncture. If interested in giving or receiving acupressure, please keep in mind that certain acupressure points, if used during pregnancy, can cause difficulties in child-birth.
This information was paraphrased from the textbook "Accupressure for Everybody", authored by Cathryn Bauer, ISBN 0-8050-1579-5.