The Trial balance provides a list of all the Debits and Credit balances in the system at any chosen date. As all journals have two sides (double entry accounting) the trial balance balancing provides comfort that the financial system is working. The system does not allow the saving of any journal that is not balanced.
The report looks back to the last closed period in the system, uses the balance for every account at that time and then adds all transactions since then.
If you find the Trial Balance is out of balance
For each account a figure is either in the Debit or the Credit column depending on the value.