Original Medicare, Part A and B, pays for many of your health-care services and supplies, but it doesn’t pay for everything. That’s why you may want to consider getting a Medicare Supplement plan, also called Medigap. Unlike Original Medicare, a Medicare Supplement plan is offered through private insurance companies. These Medigap plans help pay some of the hospital and medical costs that Original Medicare doesn’t cover, such as copayments, coinsurance, and yearly deductibles.

Some Medicare Supplement plans also help pay for a few services that Original Medicare doesn’t cover, such as emergency overseas travel coverage or Part B excess charges. Two out of ten Medigap plans include a yearly out-of-pocket limit, which Original Medicare doesn’t include. Basically, a Medigap policy fills the “gaps” in Original Medicare coverage.

Here’s an overview of how Medicare Supplement plans work, the types of benefits they cover, and how to enroll.