A co-pay or co-payment is a flat fee partial payment you make towards a medical service, such as $30 for an office visit, with the insurance company paying the remainder of the covered medical charges.

Coinsurance is when you pay a fixed percentage of the cost of medical care after the deductible is met. For example, a health plan might pay 80% of the allowable charge, with you paying the remaining 20%. The amount paid by the insured person is called the coinsurance amount.

Health insurance companies control costs by using a "pre-existing condition" clause which excludes the coverage of a medical condition that existed before you purchased the health insurance plan.