The deductible is the amount you pay every year in eligible medical services and medications before your insurance plan goes into effect. If your deductible is $250, you pay $250 out of pocket in eligible medical costs before insurance payments start.
Coinsurance is the portion of your medical costs you are required to pay after your deductible is met. For example, if your coinsurance is 20%, you pay 20% of your eligible medical expenses, and your insurance company pays the remaining 80%.
The copay (copayment) is the fixed fee you pay every time you go to the doctor or fill a prescription. Some visits may not require a copay. Many plans pay 100% for preventative care and annual checkups.