Continuous Positive Airway Pressure (CPAP) is a medical device used to treat sleep apnea, a condition where breathing repeatedly stops and starts during sleep. CPAP works by delivering a constant stream of air pressure through a mask worn over the nose or mouth, keeping the airway open and preventing interruptions in breathing. CPAP is considered a highly effective treatment for sleep apnea and can improve symptoms such as snoring, daytime sleepiness, and difficulty concentrating.