PayPal Website Payments Pro allows transactions to take place on the merchant's e-commerce store for credit card payments using the Direct Payment API feature, or in three clicks for buyers who decide to pay directly from their PayPal accounts using the Express Checkout Feature. In effect, with this system PayPal is not only serving as the payment gateway but the credit card processor as well.

Express
Checkout helps buyers with PayPal accounts pay for items in
just three clicks on a merchant's website. The buyer initiates
and approves PayPal payment earlier in the checkout process,
and shipping and billing information is sent immediately from
PayPal to the merchant website. For buyers who don't have
PayPal accounts, Direct Payment API lets merchants accept
credit card transactions just as they would with traditional
merchant accounts. The buyers simply enter their credit card
details directly on the merchant website. Payments are processed
through the PayPal system on the back end, and PayPal remains
invisible to the buyers.
Website Payments Pro also includes Virtual Terminal, a new feature that supports phone, fax and mail orders by providing merchants with an online interface to manually enter credit card transactions through the PayPal system.
Simply follow the following steps to accept PayPal Website Payments Pro today!
Customers who don't have an existing PayPal account, go to PayPal and click the "Sign Up Today" link. Follow the instructions on the PayPal site to set up a Business Account.
Customers who already have a Personal or Premier account, go to PayPal and click the "Sign Up Today" link. Follow the "Upgrade your account" link to upgrade to a Business account. If you haven't already, add a bank account to become a Verified member. Follow the instructions on the PayPal site. This process may take 2-3 business days.
To run test transactions, change the Transaction Type to "Test". You are required to set up a Sandbox account at PayPal Developer Center for testing. To test Direct Payment, use the credit card numbers below or use an actual card details (no money will be taken in test transactions):