(BPT) - Navigating Medicare can be challenging. In fact, according to a 2017 UnitedHealthcare survey, nearly 40 percent of Medicare beneficiaries find the program confusing. Learning the basics can help you cut through the confusion and make an informed decision about which coverage option may be the right fit for you.

Here's a quick guide to five important Medicare terms to help prepare for the upcoming open enrollment period. What is open enrollment, you ask? Well, read on.

1. Open Enrollment Period

If you are already enrolled in Medicare and want to make changes to your health plan, you can do so during the annual open enrollment period, which runs from October 15 to December 7. For most people, this is the one opportunity each year to make changes to your Medicare coverage.

Changes made during this year's open enrollment period take effect on January 1, 2018.

2. Original Medicare

Original Medicare is made up of Part A and Part B and is offered by the federal government. Simply put, Part A helps cover services such as inpatient care at a hospital or a skilled nursing facility. Part B helps cover doctor's office visits and outpatient physical and occupational therapy services.

According to Dr. Efrem Castillo, Chief Medical Officer for UnitedHealthcare Medicare & Retirement, "Original Medicare generally covers 80 percent of health care costs, leaving you responsible for paying the remaining 20 percent. It also does not have an out-of-pocket maximum, meaning that if you have unexpected health care costs, you could end up with a hefty bill."

Original Medicare does not cover things like prescription drugs, long-term care, hearing aids and the exams needed for fitting them, or routine dental or vision care.

3. Medicare Advantage

Medicare Advantage plans, also known as Medicare Part C, are offered by private insurance companies. Medicare Advantage plans combine Medicare Parts A and B into one plan (which means you only need to carry one card), and can offer additional benefits such as vision, hearing, dental and even gym memberships. Most plans also provide prescription drug coverage.

In addition to the all-in-one coverage, Medicare Advantage plans also have an annual out-of-pocket maximum, making it easier for you to estimate your health care costs, even when facing an unforeseen health event.

4. Medicare Supplement Insurance (Medigap)

A Medicare Supplement policy is also known as Medigap and is offered by private companies. It can help pay for some things not covered by Original Medicare, such as copays, coinsurance and deductibles. Medigap plans typically have a higher monthly premium but little or no out-of-pocket costs when you access care. However, Medigap plans don't cover prescription drugs, so you would need to enroll in a separate Part D plan.

5. Medicare Part D

Medicare Part D helps cover prescription drugs. Castillo explains, "You have two options for prescription drug coverage. Either enroll in a standalone Part D plan, or you can get drug coverage through most Medicare Advantage plans." Make sure that the plan you select covers the prescription medications you need.

To learn more, visit UHCOpenEnrollment.com.