Medicare Advantage (MA) is a United States health insurance program of managed health care (either a preferred provider organization (PPO) or health maintenance organization (HMO)) that serves as a substitute for Original Medicare Parts A & B benefits. Medicare Part A provides payments for inpatient hospital services excluding those of physicians and surgeons. Part B provides payments to physicians and surgeons, as well as for medically necessary outpatient hospital services (such as ER, laboratory, x-rays, and diagnostic tests) and certain durable medical equipment and supplies. Original Medicare claims payments are processed through the Centers for Medicare Medicaid Services (CMS.) In contrast, Medicare Advantage is offered by commercial insurance companies and HMO and PPO corporations who receive compensation from the federal government but do not process claims through the CMS.