Medicare Advantage, also known as Medicare Part C, is a Medicare plan sold by private insurance firms. Medicare has signed a contract with these companies to cover original Medicare (Part A and Part B), along with additional benefits, such as prescription medications, hearing, vision, or dental care. The coverage can vary a lot, depending on the plan and provided company. In fact, you may choose what additional benefit to have. The two most popular Medicare Advantage plans are the Preferred Provider Organization and the Health Maintenance Organization. The next sections will show you more about the differences between these two plans.