This year's enrollment period for 2011 Medicare coverage extends from November 15 to the end of the year. There are lots of changes in the various insurance programs that collectively make up Medicare. Experts say it's well worth the time to make sure your 2011 coverage remains the best deal for you.

There are four "letter" parts of Medicare:

A is for hospital services, and B is for physician, out-patient, and equipment costs. Together, parts A and B make up basic Medicare. Part C is for Medicare Advantage insurance, which includes A and B and, for most plans, prescription drug coverage. Part D is for stand-alone prescription drug coverage.

There also are a dozen Medigap policies that cover, to varying degrees, things that aren't covered in basic Medicare. Some Medicare Advantage and Medigap policies include vision and dental coverage, which is not provided in basic Medicare. If you want to supplement basic Medicare, you would chose either a Medicare Advantage plan or a Medigap policy.