Biofeedback is a treatment technique in which people are trained to improve their health by using conscious and subconscious signals from their own bodies. Psychologists use it to help tense and anxious clients learn to relax. Specialists in many different fields use biofeedback to help their clients cope with pain. Both clients and practitioners use it to gauge and direct the progress of treatment. For clients, the biofeedback device allows them to "see" or "hear" activity inside their bodies.