Co-payments are fixed dollar amounts (for example, $15) you pay for covered health care, usually when you receive the service
Co-insurance is your share of the costs of a covered service, calculated as a percent of the allowed amount for the service. For example, if the plan's allowed amount for an overnight hospital stay is $1,000, your co-insurance payment of 20% would be $200. This may change if you haven't met your deductible.
The amount the plan pays for covered services is based on the allowed amount. If an out-of-network provider charges more than the allowed amount, you may have to pay the difference. For example, if an out-of-network hospital charges $1,500 for an overnight stay and the allowed amount is $1,000, you may have to pay the $500 difference. (This is called balance billing.)
The plan may encourage to use participating providers by charging you lower deductibles, co-payments and co-insurance amounts.