Available Balance and Current Balance?

Your bank has allowed you an overdraft. It is the difference between your available balance and your current balance. Your current balance is the actual amount of money that is yours and you have saved in your bank account.

Its both good and bad, because now you can spend more but you will have to pay interest on your overdraft if you use it.

Do you not keep a separate check register and track all your checks and debit transactions? How would the bank know about checks or debit card transactions that have not hit the bank yet.?

The current balance is the balance reflecting all transactions. The available balance reflects pending transactions that have not yet posted. This could include deposits or holds on funds due to pending debit authorizations.