A CPAP (Continuous Positive Airway Pressure) machine is a medical device used primarily to treat sleep apnea. It delivers a constant stream of air through a mask to keep the patient's airways open during sleep, preventing pauses in breathing and ensuring continuous oxygen intake. CPAP machines help reduce snoring, improve sleep quality, and decrease the risk of health complications associated with untreated sleep apnea. They are commonly used in both home and clinical settings.