Compound interest is an interest that arises when interest is added to the principal everytime the interest is due, so the total amount will be calculated together to earn next interest. The addition of interest to the principal to get another interest is called compounding. Banks usually apply this kind of interest rate where your savings amount will grow based on that interest period. For example, a saving with $1000 initial principal and 1% interest per month would have a balance of $1010 at the end of the first month, $1020.1 at the end of the second month, and so on.
This compound interest also used as a loan interest. This compound interest calculator is a simple calculator that will calculate the future value of your savings or loan amount based on daily, weekly, quarterly, semi-annually and annually compounded period. And you can also see how the total interest applied to your savings or loans based on that compounded period.