A password is a secret word or string of characters that is used for user authentication to prove identity, or for access approval to gain access to a resource (example: an access code is a type of password). The password should be kept secret from those not allowed access.

User names and passwords are commonly used by people during a log in process that controls access to protected computer operating systems, mobile phones, cable TV decoders, automated teller machines (ATMs), etc. A typical computer user has passwords for many purposes: logging into accounts, retrieving e-mail, accessing applications, databases, networks, web sites, and even reading the morning newspaper online.