Variable Interest Rate
This is simply an interest rate that varies (goes up and down) depending mostly on other market conditions. For example when you take out a loan you might have an option for a variable or a fixed interest rate. If you believe that the interest rate is currently higher then it should be, then you should take the variable rate as it will descrease with market rates. If you believe that the current interest rate is relatively low then the fixed rate would be the best choice as when other market rates increase in the future you will still be paying the lower rate.