If you have done any type of online shopping, you will most likely have had to input your credit card’s CVV. The CVV is the three digits on the back of your card (four on the front if you have an American Express card), which act as an anti-fraud measure.

https://uk.finance.yahoo.com/news/why-credit-cards-cvv-number-085325369.html?soc_src=social-sh&soc_trk=tw