Double entry refers to an accounting concept whereby asset = liability + owner's equity. 

The double-entry system of accounting or bookkeeping means that for every business transaction, amounts must be recorded in a minimum of two accounts. This system also requires that for all transactions, the amounts entered as debits must be equal to the amounts entered as credits. For instance, a person enters a transaction of borrowing money from the bank. So, this will increase the assets for the cash balance account, and simultaneously the liability for loan payable accounts will also increase.