Personal identification number

Personal identification number (PIN). A personal identification number is a combination of numbers, letters, or both that you use to access your checking and savings accounts, credit card accounts, or investment accounts electronically.

You also need a PIN to authorize certain debit card purchases as well as for identification in other situations, such as accessing cell phone messages.

A PIN is one way to help protect your accounts against unauthorized use since presumably no other person would know the four- to six-letter code you have chosen. PINs are not foolproof, however, if you don't take steps to ensure that your code remains private.