Card Verification Value (CVV) is a three digit number printed on the credit/debit card. It is also known as Card Security Code (CSC). Usually, Visa, Master card and Discover debit/credit cards have CVV numbers. CVV numbers are used when PIN (Personal Identification Number) cannot be used because of some security reasons.
Remember, whenever an online merchant ask you to enter CVV number then you do not need to enter PIN (Personal Identification Number). So do not enter both CVV and PIN to a single merchant payment. It is a group of three digits on the signature strip and you can find CVV number on the back side of your credit/debit card.
How to find CVV number on credit card-
Turn your card to signature side.
On the signature strip, you can find a code printed on it.
Now you can find three or four digits which are highlighted (See screenshot). That three or four digits code is your CVV or CSC number.