Health insurance offers assistance in paying for the high cost of medical care in the United States. Health care plans can be purchased either individually or through an employer, and some plans are more comprehensive than others. General categories of plans include: HMOs, or health maintenance organizations, where you usually must go first to a primary care physician; PPOs, or preferred provider organizations, where you might have more flexibility in choosing your physician; and major medical plans, which generally only provide coverage for medical emergencies or higher-cost treatments once you have exceeded an expensive deductible. There are a series of rules and laws governing health insurance in the United States. To learn more about the types of policies and protections available to you, refer to the articles in this section.