Banks make money when they loan money. Interest adds up on large loans over time.
Not specifically identified as a loan, banks make money from interest they charge on credit cards. Interest rates up to 21% bring in a lot of money for banks.
Some banks charge fees when a debit or credit card is used to make a purchase at a retail store. This fee is called an interchange fee.
Investment banks make money by providing financial advice, tax advice, corporate bonds/loans, and brokering shares, products, and currencies.