In order to take online payment for your goods or services you need the services of a payment services provider. Once your customer has decided on a shopping basket of products they are passed seamlessly from your site to that of the payment services provider where they will be asked for their credit card number and security details. The PSP will then check the number to make sure the customer's card is valid. If all is well then the customer will be charged the value of the goods and services in their shopping basket and then redirected back to your site. If all is not well and there is a problem with the transaction then the customer will not be charged but will be redirected back to a page on your site that tells them that the transaction was not successful.