What is the main feature of a Health Maintenance Organization (HMO) plan?

HMO (Health Maintenance Organization): A managed care plan emphasizing coordinated care and cost control. KEY FEATURES: Requires choosing a PRIMARY CARE PHYSICIAN (PCP) who coordinates care; REFERRALS from the PCP usually required to see specialists; coverage generally LIMITED TO IN-NETWORK providers (out-of-network care typically not covered except EMERGENCIES); lower premiums and out-of-pocket costs than less restrictive plans; emphasis on preventive care; CONTRAST: PPO (Preferred Provider Organization) — more flexibility, no PCP/referral requirement, can use out-of-network (at higher cost), higher premiums; EPO (Exclusive Provider Organization) — in-network only like HMO but usually no referral requirement; POS (Point of Service) — hybrid (PCP/referrals but some out-of-network coverage); HMOs trade flexibility for lower cost and coordinated care; understanding HMO features (PCP, referrals, in-network restriction) and how they differ from PPO/EPO/POS is fundamental health insurance exam content.