What is Paypal payment?

Payment by Paypal is a secure SSL payment method. After creating your Paypal account on www.paypal.com, simply add your credit card number or associate one of your bank accounts once and for all. The plus: Paypal is free to pay for your purchases on thousands of sites!

Then it's very simple:

During payment, you are redirected to the Paypal server.
You simply use your email and your Paypal password to make your purchases, you do not communicate your banking information because everything is centralized by Paypal!