Covers things like inpatient hospital Stays, home health care and some skilled nursing facility care 

Covers things like doctor visits, outpatient services, X-rays and lab tests, and preventive screenings.

Private health insurance companies offer Medicare Advantage plans, also known as Medicare Part C. You're provided the coverage of Original Medicare plus extra benefits and protection.

Part A+B+D=C

Medicare Part D is outpatient prescription drug coverage.

To get drug coverage, you must join a Medicare approved plan, such as a Medicare Advantage plan with drug coverage or a standalone Medicare presicription drug plan