Recently we integrated Paypal Express Checkout payment gateway to Customer Magento website. In magento allow either paypal standard or Paypal express checkout from admin configuration.
The PayPal Express Checkout, customers are transferred to PayPal to approve the use of PayPal and then returned to our website to complete their order. Customer logs in to their account and confirms their postal address and billing information that PayPal has stored. Customer clicks Continue to use PayPal to pay for their purchase. Customer is transferred back to our website to review their order and complete the checkout process.