Preferred provider organizations are a type of health plan. PPOs have a network of doctors, hospitals, and other providers who have agreed to charge less for plan members. Members of the health plan have access to a list of providers in the network by name and location. Generally with a PPO, you do not need a referral from your primary care provider when you want to see a specialist. With PPO coverage, you may also choose to seek care from providers that do not participate in the plan's network. However, going outside the network comes with additional costs.