Interest Rate: It is the annual rate which is used to calculate your monthly payments and is the cost to you for your loan.
APR - the annual percentage rate is an implied annualized rate and includes all the other costs of taking a loan. The most common cost APR includes is an origination fee (a one-time fee charged by the online lender which is deducted from the loan proceeds).
The monthly payments are still calculated using only your interest rate, not APR.
Interest is accrued daily on your outstanding principal balance even though you are making monthly payments.