You can usually choose between a flat interest rate or a monthly rest interest rate.
With a flat interest rate, the total interest payable at a fixed rate for the entire repayment period (loan tenure or loan tenor) is calculated in advance and added to the loan principal. The resulting amount is divided by the number of months in the repayment period, to arrive a fixed equal monthly repayment amount.
With a monthly rest interest rate, the rate is variable, and the interest charge for each month is calculated based on the outstanding amount of loan principal. You will be required to repay the interest and a portion of the principal every month.
A rest rate will usually work out to be less expensive in total than a flat rate, even when the flat interest rate is lower than the rest interest rate.