CVV (Card Verification Value) is a security authentication code for the card, typically consisting of 3 digits. The 3-digit number displayed on the back of the card is the CVV security code.
It acts as a "second password" for your card, specifically used to verify online payments (card-not-present transactions). To ensure your account security, please do not disclose card information, such as the card number, expiration date, or CVV code, to others.