Medicare is a federal health insurance program for individuals 65 and older, as well as certain younger individuals with disabilities. Eligibility is typically based on work history and Social Security benefits, but some people may qualify through a spouse or other special circumstances.

Medicare Part A is often available at no cost to individuals who have worked and paid Medicare taxes for a required period, typically at least 10 years (40 quarters). This means that most people who have contributed to the Medicare system through payroll taxes during their employment do not have to pay a monthly premium for Part A coverage. However, those who do not meet the work requirements may still be eligible to enroll but will need to pay a premium.

On the other hand, Medicare Part B generally requires a monthly premium, which varies based on income and is adjusted annually. In addition to the premium, individuals enrolled in Part B may also be responsible for deductibles and coinsurance when receiving covered medical services.

Medicare Advantage plans are offered by private insurance companies and serve as an alternative to Original Medicare by combining coverage into a single plan. These plans operate within a network and may have specific rules for accessing services, such as requiring referrals or using designated providers.

Medicare Part D provides prescription drug coverage through private insurance companies approved by Medicare. It helps lower medication costs and protects against high drug expenses.