Medicare Part C, also known as "Medicare Advantage", is a type of health insurance plan offered by private insurance companies and approved by Medicare. It's an alternative to traditional Original Medicare (Parts A and B) and typically includes all the benefits covered under Parts A and B, as well as some additional benefits like routine dental, vision, and hearing care.

Medicare Advantage plans often have a network of providers and may require you to use in-network healthcare providers to get covered services. Some plans also require you to get a referral from your primary care doctor before seeing a specialist. In exchange for these restrictions, Medicare Advantage plans tend to have lower out-of-pocket costs on a month to month basis while keeping coverage some deem comparable to Original Medicare. However, the annual maximum out of pocket expenses (MOOP) can be much higher in the event you need health services.

It's important to note that if you enroll in a Medicare Advantage plan, you are still enrolled in Medicare (albeit a private version with added restrictions) and will continue to pay your Part B premium, and you may have to pay an additional premium for your Medicare Advantage plan.  It can be difficult to leave any plan and move to another plan if you have substantial health history.