A Health Maintenance Organization (HMO) is a type of health insurance plan that provides a range of medical services to its members for a fixed monthly fee. Members typically choose a primary care physician (PCP) who coordinates their healthcare and refers them to specialists when needed. This model emphasizes preventive care and often requires members to use a network of doctors and hospitals. HMOs aim to control healthcare costs while ensuring access to necessary services. They often have lower premiums and out-of-pocket expenses compared to other insurance plans, but they may limit choices in providers and require referrals for specialized care.