The card validation code is a security number, which is existing on every credit card.The number is designed to determine the identity and for fraud prevention. It is located on back of you credit card (as indictated in the picture).
Where do I find my card validation code (CVV/CVC/CID)?
Visa, Master Card: The last 3 digits of the number in the signature field on the back of the card.
Amex: The four-digit number right above the embossed on the card front.