Terms of Use:

Overdrafts occur when you spend more than you have on balance in your account.  This spending can occur from online bill payment, check writing, use of an ATM, or purchases made with a debit card (sometimes called a check card).

While it's important to maintain your balance in your account to avoid overdrawing it, once in awhile you may accidentally overdraw your account.  Depending on the arrangements you have with your financial institution, you may have overdraft or bounce protection.  This often means that you can overspend the amount you have in your account, yet be aware that there are fees attached to doing so.  These fees amount to a short-term loan, and the financial institution is repaid when you make your next deposit.

According to a study by the Center for Responsible Lending of 5,000 American households, almost half of all overdraft loans are caused by ATM withdrawals or by debit card transactions at stores, restaurants, gas stations and other merchants.  Paper checks caused one quarter of overdrafts, and another quarter of overdrafts were caused by online bill payments.   

Pay careful attention to your account balances in order to avoid paying more for that next purchase than you had intended.