It is card which gets generated online for a specific amount. It can be used once. Amount is deducted from Debit account so debit account is mandatory. It can be used once. If the Virtual card is left with some amount after first usage money is credited back within 45 day(MAX). Presently 2 types are created VISA and Master.
It helps internet fraud as it can be used once. You can say in net it is preloaded card with specific amount having no physical existence and can be used once. Prelaoded card can be used many times and have physical existence.