A Health Maintenance Organization (HMO) is an organized plan that provides for your health care. Some plans are very tightly structured so that all care is provided by the HMO's employees in the HMO's hospitals or clinics, while other plans are cooperative agreements among independent doctors, hospitals and other health care providers.
A person who belongs to an HMO program will have access to a "primary care provider" who knows the person's personal, family, social, and financial situations well enough to coordinate his/her care in an effective way that will use fewer services. Your primary care provider is available to see you for basic care and for an illness. Primary care providers run tests or prescribe treatments before passing you on to a specialist.

Types of HMOs:

Staff model: in the staff model, physicians are salaried and have offices in HMO buildings. Physicians are direct employees of the HMOs. This model is an example of a closed-panel HMO, meaning that contracted physicians may only see HMO patients.

Group model: in the group model, the HMO does not pay the physicians directly, but pays a physician group. The group then decides how to distribute the money to the individual physicians. This model is also closed-panel.

Open-panel Model: Physicians may contract with an independent practice association (IPA), which in turn contracts with the HMO. This model is an example of an open-panel HMO, where a physician may maintain his own office and may see non-HMO members.

Network model: in the network model, an HMO will contract with any combination of groups, IPAs, and individual physicians. Since 1990, most HMOs run by managed care organizations with other lines of business use the network model.