Loan agreement has many things as part of terms which are mutually agreed between the parties. One of such terms is the time period for repayment of principal amount and interest if any. It can be lump sum repayment of amount or it can be in shape of installments.
Usually what happens these days is that the borrower is liable to return the loan in shape of installments which are payable after certain period of time. Even when any such installment is delayed then there is penalty on that.