HMO and PPO are not Medicare's inventions. They are the two familiar shapes of managed care, and when a Medicare Advantage plan wears one of those labels it is telling you how it handles two things: who you may see, and what happens if you go outside that group. Everything else people argue about follows from those two rules.
What the HMO rule is
An HMO arrangement is built around a defined network and generally expects care to be coordinated through a primary care physician, with a referral before a specialist. Outside the network, other than in an emergency, the plan generally does not pay. That is a genuine constraint and it is also the mechanism that makes the arrangement cheaper to run, which is why the label matters more to somebody with established specialists than to somebody who has not seen one in years.
What the PPO rule is
A PPO arrangement also has a network but pays something outside it, usually at a worse rate, and typically does not require a referral to see a specialist. The looser rule costs more, one way or another, because somebody is paying for the flexibility. Neither shape is better in the abstract: the question is whether the doctors a particular person already uses are inside the network, and that is a fact about their address rather than about the label.
Why this page names no plan
Which networks exist, who is in them and what any of it costs are plan-level facts that change annually and by county, and stating them is marketing content under the federal rules governing this market. This site publishes what CMS publishes instead: how many people in each state hold a Medicare Advantage or other health plan at all. Medicare's own plan finder is where the network question gets answered, because it asks for the providers first.
Questions people ask about medicare advantage hmo plans
Do all Medicare Advantage plans use one of these two shapes?
Not all. Other arrangements exist, including private fee-for-service and the Special Needs categories, each with its own rules.
Does an HMO ever pay outside its network?
Emergency and urgently needed care is treated differently. Medicare's own pages are the authority on the detail.
Which is better?
Neither, in general. It depends on whether your existing doctors are in the network, which is a question about your address rather than about the label.
Where do I check whether my doctor is in a network?
Medicare's plan finder takes a list of providers, and your State Health Insurance Assistance Program will help you read the result, free.