HMO (Health Maintenance Organization)
Select a primary care doctor from the plan network and he or she directs your medical care. This doctor gives you referrals when you need to see a specialist, like a dermatologist. Also, with an HMO, you must go for medical care within your plan’s network – or you won’t be covered (except for emergencies).
PPO (Preferred Provider Organization)
Visit any doctor – in the network or out as there are no referrals. Moreover, you don’t have to pick a primary care doctor.