The CVV is a 3 or 4 digit code embossed or imprinted on the reverse side of Visa, MasterCard and Discover cards and on the front of American Express cards.
The CVV2 is the last 3 digits after the credit card number on the back of the card in the signature area.
The CVC2 is the last 3 digits after the credit card number on the back of the card in the signature area.
The Discover CIDis the last 3 digits after the credit card number on the back of the card in the signature area.

The AmEx CID is printed on the front of the card, above and to the right of the embossed card number