There are 3 – 4 separate parts to Medicare which become available to you once you are 65. If you are already getting social security benefits when you turn 65, your Medicare Part A starts automatically. If you are not already receiving Social Security benefits when you turn 65, you should sign-up for medicare several months before your 65th birthday.
Part A, or hospital insurance, covers inpatient hospital care and certain follow-up care. You have already paid for this as part of your Social Security taxes while you were working.
Part B, or medical insurance, pays for physicians’ services and some other services not covered by Part A. This coverage is optional, and you must pay for it in monthly premiums.
Medicare Advantage (Part C) plans are available in many areas. People with Medicare Parts A and B can choose to receive all of their health care services through one of these provider organizations under Part C. These organizations are often referred to as "Medicare HMOs"
Part D, or prescription drug coverage, pays for prescription drugs. This insurance is also optional and requires that the recipient pay monthly premiums. If you have a limited income, you may qualify for extra help paying the premiums, deductibles, and prescription co-payments.