A rate - is what you pay monthly on borrowed money, it is expressed as a percentage of the borrowed sum. A fixed rate - is a rate of interest that stays the same and never fluctuates. A variable rate - is a rate of interest that is linked to the prime interest rate, it fluctuates or is adjusted periodically in accordance with prevailing market conditions, which affect the prime rate. The Prime Rate - this is the minimum interest rate charged by a commercial bank on short-term business loans to best rated customers or corporations.