Carpal tunnel syndrome occurs when the median nerve, which runs from the forearm into the palm, becomes compressed as it passes through the carpal tunnel in the wrist. Symptoms include pain, numbness, and tingling in the hand and fingers. While repetitive wrist motions were originally thought to be the primary cause, any condition that puts pressure on the median nerve can lead to carpal tunnel syndrome. Diagnosis involves tests like Phalen's maneuver and electromyography, while treatment ranges from wrist splints and injections to surgery.