You simply deposit cash on your debit card and you're able to use the card to make Internet payments or other type of payments like you could do with any regular credit card.
Prepaid debit cards are ideal for people that don't have a bank account or would like to have optimal control on their spending behavior, because the only money you can spend is what you've deposited onto your debit card account.
Added to that you can choose a debit card from well known card issuers so you know you're in good hands, the Visa prepaid card or Mastercard prepaid card are great options for people that would like to be in control over their spending behavior.