Medicare is a federal health insurance program in the United States that primarily covers individuals who are 65 and older, as well as certain younger individuals with disabilities or specific medical conditions. The program helps cover healthcare costs, including hospital stays, doctor's visits, prescription drugs, and some preventative services. There are different parts of Medicare, including Part A (hospital insurance), Part B (medical insurance), Part C (Medicare Advantage plans), and Part D (prescription drug coverage). Medicare research may focus on topics such as healthcare utilization, cost effectiveness, coverage gaps, and health outcomes for Medicare beneficiaries.