Banks pay interest on savings accounts (usually) and checking accounts (sometimes). If you pay into an escrow account with your mortgage, the escrow bank may pay interest. If someone borrowed money from you and paid back more than the original amount, that is also considered interest. If you have an investment account with a brokerage, some of your investments might have earned interest.
This would be reported on a 1099-INT form sent to you by the bank. Banks are not required to sent the 1099-INT if the interest is less than $5, but you are still required to report even small amounts. (A private borrower will not send you a 1099-INT, but if you make a loan to someone else and charge interest, you are required to keep your own accurate business records.)
In the case of a brokerage account, you might have received a "combined tax statement" that includes a 1099-INT for interest, a 1099-DIV for dividends, and a 1099-B for sales of stocks and other capital investments. If you have a broker account, you may be able to import the combined tax statement, in which case the interest is already imported into the program and you don't need to list it again, although you may need to list other items of interest.
