Medicare insurance is a U.S. federal program that provides health coverage primarily to individuals who are 65 or older, as well as to younger people with certain disabilities or medical conditions. It is divided into four parts: Part A (hospital insurance), covering inpatient hospital stays and some home health care; Part B (medical insurance), covering outpatient care, doctor visits, and other medical services; Part C (Medicare Advantage), an alternative to Original Medicare that allows beneficiaries to enroll in private health insurance plans; and Part D, which covers prescription drug costs. Medicare helps manage healthcare costs but does not cover all expenses, including most long-term care.