I want buy Minecraft Premium account but I don't know what is CVV what i need type in there?

If you look on the back of your credit card you will see the credit card number and some additional numbers (usually 3-4). The first 16 is the credit card number and then you see 3 or 4 additional numbers. That's the cvv number or security code. It's usually in a box. It's sort of an additional safety feature since cameras can capture your credit card number but it usually can't get your cvv number since its on the back and you usually don't flip the card over.