What does Key mean?

Pertaining to credit card related terminology a key is the main constituent in close relationship with the encryption method of the card. The key is useful to keep personal data safe in any transaction process which implies the use of a credit card, and the most common type of encryption is the DES encryption (192 bit). For example, when the details of your credit card need to be transmitted during an online transaction, all of the personal details are encrypted during this process, so that no third party has access to any of the information.