A debit either expands an asset or reduces a liability; a credit either reduces an asset or expands a liability. Based on the principle of double-entry, each financial transaction matches a debit and a credit.
When cash is put down in a bank, the bank is claimed to “debit” its cash account on the asset side and “credit” its down payment account on the liabilities side. In this issue, the bank is debiting an asset and crediting a liability, which means that both expand.