Medicare is divided into four parts: Part A, Part B, Part C and Part D.
Original Medicare consists of Part A (Hospital insurance) and Part B (Medical insurance).
Medicare Part A is free mostly to all people without premium. The payment schedules are usually decided by Medicare. The organization providing health care is not permitted to charge more than the approved amount by Medicare. Some people have Part A and some have both Part A and Part B. Original Medicare covers most of the services but not all. You can buy Medigaps policy to fill the gaps in Original Medicare.
You can join Medicare Prescription Coverage to cover the cost of prescription drugs.
You pay for Copayments, coinsurance and deductibles which may apply on each of the above services
If you are covered by Medicare Advantage Plan like a HMO or PPO or supplement insurance (Medigap policy), the cost may differ.
You can avail the enrollment for Part B anytime in seven month period. This seven month period starts three months before you are 65 and ends three months after the month you complete 65 years of age.
If the initial enrollment period is over and you did not enroll for Medicare Part A and /or Medicare Part B, you can enroll from January 1-March 31 each year.
But you will have to pay higher premium for delayed enrollment.