PIN - Personal Identification Number
Personal Identification Number is used as a password in several entities including ATM Card, Debit Card, Credit Card, Mobile SIM card etc. It is the number which is hidden from the manufacturer or provider of a card and is known only to the user. It allows user to make transaction in a secure manner, as required.
The ATM or Credit Card comes with the PIN Number in a secret envelope, which is only known to the user and the system. In case you need to withdraw money from an ATM, a Personal Identification Number must be entered correctly. There are several cards that allow you to swipe them, without requesting a Personal Identification Number.
In case the user forgets the PIN, it can only be recovered or reissued by the provider of the card. This is done to avoid any kind of misuse of the card.