A contract between an insurance provider (e.g. an insurance company or a government) and an individual or his/her sponsor (e.g. an employer or a community organization). The contract can be renewable (e.g. annually, monthly) or lifelong in the case of private insurance, or be mandatory for all citizens in the case of national plans. The type and amount of health care costs that will be covered by the health insurance provider are specified in writing, in a member contract or "Evidence of Coverage" booklet for private insurance, or in a national health policy for public insurance.
Early hospital and medical plans offered by insurance companies paid either a fixed amount for specific diseases or medical procedures (schedule benefits) or a percentage of the provider's fee. The relationship between the patient and the medical provider was not changed. The patient received medical care and was responsible for paying the provider. If the service was covered by the policy, the insurance company was responsible for reimbursing or indemnifying the patient based on the provisions of the insurance contract ("reimbursement benefits"). Health insurance plans that are not based on a network of contracted providers, or that base payments on a percentage of provider charges, are still described as indemnity or fee-for-service plans.
Public insurance cover increased from 2000–2010 in part because of an aging population and an economic downturn in the latter part of the decade. Funding for Medicaid and CHIP expanded significantly under the 2010 health reform bill. The proportion of individuals covered by Medicaid increased from 10.5% in 2000 to 14.5% in 2010 and 20% in 2015. The proportion covered by Medicare increased from 13.5% in 2000 to 15.9% in 2010, then decreased to 14% in 2015.
Costs for employer-paid health insurance are rising rapidly: between 2001 and 2007, premiums for family coverage have increased 78%, while wages have risen 19% and inflation has risen 17%, according to a 2007 study by the Kaiser Family Foundation. Employer costs have risen noticeably per hour worked, and vary significantly. In particular, average employer costs for health benefits vary by firm size and occupation. The cost per hour of health benefits is generally higher for workers in higher-wage occupations, but represent a smaller percentage of payroll. The percentage of total compensation devoted to health benefits has been rising since the 1960s. Average premiums, including both the employer and employee portions, were $4,704 for single coverage and $12,680 for family coverage in 2008.
In the run-up to the 2016 Democratic National Convention, the Democratic Platform Committee approved a plank supporting the addition of a public option onto the Affordable Care Act. The decision was seen as a compromise measure between the Hillary Clinton campaign who during the 2016 presidential primaries advocated for keeping and reforming the ACA, and the Bernie Sanders campaign who advocated for repealing and replacing the ACA with a single-payer Medicare for All program. The Clinton campaign stated shortly before the plank was added that as president Clinton would "pursue efforts to give Americans in every state in the country the choice of a public-option insurance plan", while Bernie Sanders applauded the decision to "see that all Americans have the right to choose a public option in their health care exchange, which will lower the cost of healthcare". The call was echoed by President Obama, who in an article for the American Medical Association stated that Congress "should revisit a public plan to compete alongside private insurers in areas of the country where competition is limited."
Employers and employees may have some choice in the details of plans, including health savings accounts, deductible, and coinsurance. As of 2015, a trend has emerged for employers to offer high-deductible plans, called consumer-driven healthcare plans which place more costs on employees; some employers will offer multiple plans to their employees.
Most aspects of private health insurance in Australia are regulated by the Private Health Insurance Act 2007. Complaints and reporting of the private health industry is carried out by an independent government agency, the Private Health Insurance Ombudsman. The ombudsman publishes an annual report that outlines the number and nature of complaints per health fund compared to their market share 
In addition to medical expense insurance, "health insurance" may also refer to insurance covering disability or long-term nursing or custodial care needs. Different health insurance provides different levels of financial protection and the scope of coverage can vary widely, with more than 40% of insured individuals reporting that their plans do not adequately meet their needs as of 2007.