Once you choose what to buy you can immediately pay with credit card, debit card or with your paypal account. All these payments come across the Paypal secure server.
You don't need a paypal account if you want to pay with credit card!
PayPal is an account-based system that lets anyone with an email address securely send and receive online payments using their credit card or bank account. It is the most popular way to electronically pay for eBay auctions and it is becoming a cheap way for merchants to accept credit cards on their on-line storefronts instead of using a traditional payment gateway.
More info about Paypal here