Part A is hospital coverage, including inpatient care, skilled nursing facility care, and hospice care.
Part B covers doctors, outpatient care, durable medical equipment, and preventive services.
Part C (Medicare Advantage) is offered by private insurers, covers everything Original Medicare covers with more predictable copays, and often adds routine hearing, dental, vision, and fitness benefits.
Part D is Medicare's prescription drug benefit and the only part requiring enrollment through a private plan to maintain creditable coverage — usually inside a Part C plan or via a standalone PDP.