Double-entry bookkeeping, also known as double-entry accounting, is a method of bookkeeping that relies on a two-sided accounting entry to maintain financial information. Every entry to an account requires a corresponding and opposite entry to a different account. wikipedia 
The double-entry system has two equal and corresponding sides known as debit and credit. A transaction in double-entry bookkeeping always affects at least two accounts, always includes at least one debit and one credit, and always has total debits and total credits that are equal. The purpose of double-entry bookkeeping is to allow the detection of financial errors and fraud.
For example, if a business takes out a bank loan for $10,000, recording the transaction would require a debit of $10,000 to an asset account called "Cash", as well as a credit of $10,000 to a liability account called "Notes Payable".
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