In a PPO Plan, you pay less if you use doctors, hospitals, and other health care providers that belong to the plan's network . You pay more if you use doctors, hospitals, and providers outside of the network.
Health Maintenance Organization (HMO) limits coverage to care from providers who are contracted with the HMO. You will have to choose a Primary Care Physician (PCP) and only see that doctor, or a referral from that doctor, in order to have coverage except for emergencies.
Gap plans are used to protect you from high deductibles or out-of-pocket maximums for hospitalizations or surgeries. An example would be a hospital coverage plan that pays up to $6,000 for your hospital stays for about $25/month.
Accident plans pay you if you have an accident. An example would be a broken limb in an accident would pay up to $5,000.