Interest is the cost of borrowing money typically expressed as an annual percentage of a loan. The money people earn on their savings is called Interest. Interest is paid to the lender by the borrower, in case of a loan or from the financial institution to the depositor, in the case of a savings account. In financial terms, it is a payment made for using the money of another i.e. borrower takes money from the lender. Interest is the cost of renting the money for the borrower and it is the income from lending money for the lender.