what is the Security Number on back of card?

The Security Number on the back of a card, often referred to as the CVV (Card Verification Value) or CVC (Card Verification Code), is a three-digit code used to enhance the security of card transactions. It helps verify that the person making the purchase has physical possession of the card. This code is not stored on the magnetic stripe and is required for online and phone transactions to reduce fraud. Always keep this number private and do not share it unnecessarily.