The AdBit Debit Card is a "Bitcoin-Powered" VISA Debit Card. What does this mean?
It means that the VISA Debit Card is directly linked with your Bitcoin-Wallet and that you can spend all your Bitcoin credits on this wallet in real money (US-Dollar, Euro, GB Pounds etc) online with a virtual debit card. In case you have got a plastic debit card you can use it in offline (real-life) shops and at ATM's.
The conversion between Bitcoins (BTC) and the real currency is done automatically by the wallet.