My friend says she owes money to the bank where she has a checking account but its not a loan?!
Suzi is right! This happens when you "overdraw" your account. Lots of people overdraw their account and get charged fees and can't pay them back! This will result on their account being "charged off". If this happens and the person is still unable to repay their debt, it will get reported to the credit bureau and a company called Chexsystems. They share info with all major banks and track negative balances on checking accounts. If your ssn is listed on Chexsystems it can keep you from being able to get a checking account at most major banks!
However if you take out/spend more money than your checking account has then you have to pay for what you over-spent and a fee!