You have a few Medicare options when buying an insurance plan. The two most popular types of plans are Medicare Supplement plans and Medicare Advantage plans. They are both sold by private insurance companies, but are very different in how they provide coverage. Medicare Supplements cover the gaps in Medicare's standard coverage and you're still enrolled in Original Medicare. There are no networks and you can see any Medicare provider. With Medicare Advantage Plans, you have networks, require prior authorization, and Medicare is no longer managing your care; the Medicare Advantage plan is now managing your care.