Mr.Dharamaraju is right. To put in a much simpler way.
Advance tax is paid over a period of time before the completion of the financial year. The amount of advance tax is determined based upon the tax outflow at year end. The payment of advance tax is in majority of the cases equal to provision.
At the end of the year when the actual tax liability is known. Advance tax and provision for income tax is knocked off and balance if more is paid and if less then shown as refund receivable from department.
You ought to consider deferred tax effect as well.