The preferred provider organization is a combination of traditional fee-for-service and an HMO. Like an HMO, there are a limited number of doctors and hospitals to choose from. When you use those providers (sometimes called "preferred" providers, other times called "network" providers), most of your medical bills are covered.

When you go to doctors in the PPO, you present a card and do not have to fill out forms. Usually there is a small co-payment for each visit. For some services, you may have to pay a deductible and coinsurance.

As with an HMO, a PPO requires that you choose a primary care doctor to monitor your health care. Most PPOs cover preventive care. This usually includes visits to the doctor, well-baby care, immunizations, and mammograms.

In a PPO, you can use doctors who are not part of the plan and still receive some coverage. At these times, you will pay a larger portion of the bill yourself (and also fill out the claims forms). Some people like this option because even if their doctor is not a part of the network, it means they don't have to change doctors to join a PPO.