The money that you pay out-of-pocket for the services that you receive. This could include anything from an office visit to the doctor, prescription medicine, an x-ray, or even a hospital stay.
Now if the money you pay is a set amount that would be called a co-payment or a copay. If the money that you pay is a percentage of the cost then that would be called coinsurance. Now depending on the plan that you have it dictates whether you have a co-payment/copay or coinsurance.