Medicare is a federal health insurance program for people who are 65 or older, or those with certain disabilities. It has four parts: Part A (hospital insurance), Part B (medical insurance), Part C (Medicare Advantage), and Part D (prescription drug coverage). Part A covers inpatient hospital stays, skilled nursing care, hospice care, and home health care. Part B covers doctor visits, outpatient care, preventive services, and medical equipment. Part C is offered by private insurance companies and provides additional benefits beyond Parts A and B. Part D covers prescription drug costs.