A Medicare Supplement Plan, also known as Medigap, is extra insurance that you can buy from a private health insurance company to help pay your share of out-of-pocket costs in Original Medicare. To buy a Medigap policy, you must have Original Medicare, which includes both Part A (Hospital Insurance) and Part B (Medical Insurance) . Medigap policies help cover out-of-pocket costs associated with Original Medicare, such as copayments, coinsurance, and deductibles. The benefits of Medigap plans are different in each plan, and there are ten different types of Medigap plans offered in most states, which are named by letters: A-D, F, G, and K-N. All Medigap policies are standardized, meaning they offer the same basic benefits no matter where you live or which insurance company you buy the policy from. However, the price is the only difference between plans with the same letter that are sold by different insurance companies. Medigap policies do not include prescription drug coverage, so if you want prescription drug coverage, you can join a Medicare Prescription Drug Plan (Part D) . It is important to note that Medicare Supplement insurance plans are not the same as Medicare Advantage plans.