A Debit card is very similar to a credit card in appearance and can usually be used in the same places and in a similar way to using a credit card. The big difference between a debit card and a credit card is that a purchase or cash withdrawel made with a debit card is automatically debited against your bank account balance. The transfer of money is made on the day of the transaction and debited directly. There is no credit involved. If you don't have the money in your account, or an overdraft facility available, you will not be able to carry out the transaction.
A huge benefit of this is that by using a debit card for your day to day purchases you will not be able to spend money you don't have. You won't be building up a debt like you would by using a credit card. It's an alternative to using and carrying cash and works in a similar way. If you don't have the money then you can't buy the item.
One disadvantage of using debit cards rather than credit cards is that you don't get the legal protection that a credit card company must provide. If you have paid for something with a debit card then you cannot contact the card company to assist with the resolution of errors, fraud or other issues. So, particularly for online and other "distance selling" purchases a credit card may offer more protection.
Think of a debit card as a plastic cheque book and you won't be too far from the truth.
