Interest income is the primary way that most commercial banks make money. As mentioned earlier, it is completed by taking money from depositors who do not need their money now. In return for depositing their money, depositors are compensated with a certain interest rate and security for their funds.
Then, the bank can lend out the deposited funds to borrowers who need the money at the moment. The lenders need to repay the borrowed funds at a higher interest rate than what is paid to depositors. The bank is able to profit from the interest rate spread, which is the difference between interest paid and interest received.