Interest rate is percentage or amount charged by the lender for the use of its money. Anybody can provide money and charge interest rate on principal amount, but its banks that do it the maximum. The banks also borrows money in form of deposits and pay you interest rate on your money. They do this practice in order to encourage the people to make deposits.
Slightly bank charge higher interest rate to the borrower than they pay to the depositor so that they can generate profit. The interest rates are not same all the time, as they are very competitive. Usually banks charge higher rate of interest to the people they consider risky.