Your interest rate is the cost you are paying the bank or lender for the loan you have taken out. If the interest rate goes up, your repayments increase, if your interest goes down your repayments will decrease. For eg. On a $700,000 loan with an interest rate of 5% on a 30yr loan term you would have weekly repayments of $867 per week. For the same loan on a 3.79% interest rate the repayments would reduce to $751 per week. The loan size is the same but the cost is lower.