Medicare is a sometimes confusing subject.  My goal in this section is to clarify it and make you aware of your rights and responsibilities.  Let's start with the basics:

Medicare is the federal health insurance program for people who are 65 or older, certain younger people with disabilities, and people with End-Stage Renal Disease (permanent kidney failure requiring dialysis or a transplant, sometimes called ESRD).  There are 4 different parts:

Part A covers inpatient hospital stays, care in a skilled nursing facility, hospice care, and some home health care.  If you've paid taxes into social security, this costs nothing.

Part B covers certain doctors' services, outpatient care, medical supplies, and preventive services.  In 2021, the premium for most people is $148.50¹ a month.  For high earners, pricing information can be found here.

Part C, also known as Medicare Advantage, is a type of Medicare health plan offered by a private company that contracts with Medicare to provide you with all your Part A and Part B benefits.

Part D is prescription drug coverage.

Since Parts A and B do not cover costs completely, most people choose a secondary plan.  In the next 2 sections, I explain what those choices are and what they cover.

Very important note 1:  if you're insured under a group plan through your employer and are only enrolled in Part A and not Part B, you have 8 months² from the time you lose your coverage to sign up for Part B without incurring penalties.  The application for part B and the form you need to bring to your employer can be found here and here.

¹ 2021 Medicare and You page 32. Publication date Dec. 1, 2020
² 2021 Medicare and You page 26.