Reimbursement is a fancy term that insurance companies made up for payment. The dictionary defines this as
1. To make repayment to for expense or loss incurred
2. To pay back; refund; repay,
Reimburse is also defined as: to repay or compensate (someone) for (money already spent, losses, damages, etc)
Technically, the money is supposed to already be paid. The insurance company is supposed to be paying their insured back a portion of what they have paid out to the doctor, hospital, contractor, electrician or whomever.
If your doctor is having trouble collecting the money, he or she may ask you to pay the bill and negotiate with your insurance company. If your doctor does not participate with the insurance company (see this http://dr-lasermed.blogspot.com/2011/09/health-insurance-101-2-participating.html ), you may very well get the check.
Your doctor’s office will often know what the insurance company is going to do. If they tell you that you are responsible for the bill, don’t argue. They know what they are talking about.
(Italics mine as is sarcasm.)