Medicare Enrollment Periods What do they really mean?

You are able to enroll in or change your Medicare plan during one or more of the following enrollment periods:

•Initial Enrollment Period (IEP)
•Medigap Open Enrollment Period
•Annual Coordinated Election Period (AEP)
•Medicare Advantage Disenrollment Period (MADP)
•Special Election/Enrollment Period (SEP)

This is the time to enroll in Medicare for the first time if you are turning 65. It is your birthday month (unless your birthday falls on the first of the month, then your birthday month is the previous month) plus the 3 months prior to your birthday month and the 3 months after your birthday month.
Medigap Open Enrollment Period is the period of time when an insurance company cannot:

•refuse to sell you any Medigap policy it sells;
•make you wait for coverage to start (pre-existing exclusion may apply)
•ask you any health questions to determine your rate
Medigap Open Enrollment lasts for 6 months. It begins on the 1st day of the month in which you are BOTH age 65 and older AND enrolled in Medicare Part B. This period cannot be changed or repeated.
October 15 through December 7 each year. New coverage becomes effective January 1.

You can do the folowing:

Return to Original Medicare from a Medicare Advantage (MA) or Medicare Advantage with Prescription Drug (MAPD) plan.
Enroll in a MA or MAPD plan
Enroll in a Part D Prescription Drug plan
Change MA or MAPD plans
Change Part D Prescription Drug Plan
January 1st thru February 14 each year. Your Original Medicare benefits will become effective the first of the month following disenrollment from your Medicare Advantage plan. Your Prescription Drug coverage will become effective the first of the month after your application has been received.

You can do the following:

Return to Original Medicare from a Medicare Advantage (MA) or Medicare Advantage with Prescription Drug (MAPD) plan.
Enroll in a Part D Prescription Drug plan if disenrolling from a MA or MAPD plan
Apply for a Medigap (Medicare Supplement) policy (medical underwriting may be required