What is a HMO?
A Health Maintenence Organization (HMO) consists of a contracted group of doctors and medical providers called  a "network" which must be managed by a Primary Care Physician. A Primary Care Physician (PCP) is selected from the network by the patient. This PCP becomes the "manager" or "gatekeeper" of all the medical treatment. All doctor visits to any other medical provider must have a referral from the PCP. Only medical treatment from within the network is covered. Patients generally only pay a "copayment" per visit. Policy details vary per insurance company.