APR refers to the annual percentage rate, and it tells you how much extra you pay over the course of a year for borrowing the money, including both the interest rate and any associated fees. If you take out a loan with a 10 percent APR, you pay $110 for every $100 you borrow for a year. Annualized rate is a rate of return for a given period that is less than 1 year, but it is computed as if the rate were for a full year. It is essentially an estimated rate of annual return that is extrapolated mathematically. The annualized rate is calculated by multiplying the change in rate of return in one month by 12 (or one quarter by four) to get the rate for the year. APR Explained: Annual Percentage Rate (APR) is the equivalent interest rate considering all the added costs to a given loan.Naturally, it is a function of the loan amount, the interest rate, the total added cost, and the terms. The APR would equal the interest rate if there is no additional costs to a given loan.