Entered Currency Balancing Account is specified at Ledger level Using ACcounting Setups window.
In Oracle a journal must be balanced in both "entered currency" as well as in "functional/converted" currency.
When foreign currency is involved then entered currency might not be in balance (debits must be equal to credits).
Then Oracle inserts additional journal lines to balance the journal in entered currency. These additioanl lines do not have an impact on functional currency.
See the attached document for an example related to foreign currency bank reconciliation.