Part C is a Medicare Advantage plan. In California, these are typically HMO plans, however, they can be PPO plans also. These plans are considered managed care, where you pick a Primary Care Physician, who belongs to one or more networks. You pick which network you want to work within. Once you’ve picked your doctor and start using the plan, you may have to get referrals to doctors and stay within that network. If you choose to go out of network, then you won’t have any coverage with the HMO’s. If you’re on a PPO, you can go out of network, by you’ll pay more for services. With Medicare Advantage plans, you have deductibles and copays as you use the plan.