The main difference between a Medicare Advantage plan and a Medicare Supplement plan is that a Medicare Supplement plan acts in addition to your Original Medicare policy. A Medicare Supplement plan will help to cover deductibles and extra co-payments that are not fully covered by Medicare A and B.
In contrast, a Medicare Advantage plan completely replaces your Original Medicare plan. These plans work in a similar fashion to a group health insurance plan and have set copays for various services and a network of doctors that participate. One major perk of a Medicare Advantage plan is that your coverage includes the costs of prescriptions, whereas with Original Medicare you would have to purchase Part D prescription drug coverage separately from an insurance company.