Just one bit of clarification -
Medicare Benefits can be accessed by either Traditional Medicare or a Medicare Advantage plan - they both cover the same benefits but are just paid in a different way. The choice is yours as to how you want to get your benefits.
Everybody on Medicare has Part A (usually free of premiums if you have worked long enough) and Part B (premium paid). Everybody needs a Part D plan if nothing else but to protect themselves from late sign-up penalties.
Some people may want a Traditional (or Original) Medicare but then one also needs some financial protection to cover the part of the medical bills that Medicare does not cover since the Traditional program has no limit to total out of pocket expenses. So that means a Medigap plan which cost premiums every month and normally these are only available at the best price when you 1st sign up for Medicare - after that period it could cost more and perhaps certain re-existing conditions may not be covered for a while.
Some people may opt for a MA plan which they can change every year during open enrollment as their needs may change. These plans have premiums, co-pays, co-insurance, deductibles and an annual out of pocket for which people know up front their financial responsibility so there is no need for any other plan to financially protect them.
Both types are governed by rules set forth by the government (CMS.gov).
This just hit the very simplest of highlights - there is a whole lot more. Medicare.gov is a great source as well as Medicare.gov - Medicare and You 2023
It's Always Something . . . . Roseanna Roseannadanna