The interest rate is the gaining that you make for keeping your money in the bank. Suppose you have $100 and the bank offers you a 5% annually interest rate. The rate (5%) means that your money will earn five percent of the value each year, so after the first year you will earn (5%)*($100) = $5 of interest just for keeping your money in your savings account. Therefore, your money will grow overtime because it is earning interest. Remember that interest can be compound (over periods) or simple (like our example).
