An explanation of benefits is a statement from your health plan that lists the services you've had and how much your plan paid toward them. The EOB also shows what charges are not covered by your health plan. That's the amount you usually have to pay.
An EOB is not a bill. However, you may get a bill for the amount that still has to be paid to the provider for the care you got.
If you see anything wrong on your EOB, call your health plan's customer service department.