Debit and Credit memos will increase or decrease the figure in the Cash account on a company's Balance Sheet. For example, if a business makes a loan payment in cash, they will be dispensing money from their bank account to the entity that issued the loan to them. Therefore, they will Credit their cash account as money is leaving their bank account.
Their Journal Entry in their business accounting records will show a Debit to Loan Payable - they reduce this Liability account by the amount of the loan they've paid. They Credit their Cash account to show that they now have less cash in the bank because of making a loan payment. In addition, they will Debit Interest Expense on the loan. This reduces the amount, in their records, of the Loan Interest they still owe.
The Debit and Credits have to jive. Therefore, their journal entry will look like this, based on a $2,000 cash payment towards the loan, which will cover principal and interest payments:
DR Interest Expense 300
Dr Loan Payable 1700
CR Cash 2000