What do current balance and available balance mean?
A current balance incorporates all transactions that have been processed to your account. This may include funds which have been deposited to the account but not yet cleared (eg. a cheque deposit) and therefore are not available for withdrawal.
Likewise, it may include funds recently debited from the account (such as Visa card authorisations) that are yet to be processed to the account.
Your available balance is the money available for withdrawal from your account.