Medicare Advantage (Part C) plans are offered by private insurance companies approved by Medicare. They bundle your Medicare Part A and Part B benefits — and usually add much more.
Requires you to use in-network doctors and get referrals to see specialists. Generally the lowest-cost option. You select a primary care physician who coordinates your care.
More flexibility — you can see out-of-network providers (at higher cost) and don't need referrals. Generally higher premiums than HMO.
The plan determines how much it will pay doctors/hospitals and how much you pay.
Tailored for specific groups: those with chronic conditions, those in certain institutions, or those who are dually eligible for Medicare and Medicaid (D-SNP).