no, you go to the website and sign up, you have to enter your credit/debit card number, or checking account number, and they keep that on file in your account (don't worry it's safe). then when you buy something and click on the "paypal" logo, it takes you to the sign in page and you sign in to paypal and click "send payment" and it charges it right to your credit card, or deducts it straight from your bank account using your debit card or checking account. it's really pretty simple and safe, I use it for ebay and anything else I find that might take paypal.
picture this....you buy something on ebay and get screwed, the person doesn't send you the product or the product is broken or complete junk or whatever and the person refuses to give you your money back. Well, if you have paypal, you have 2 lines of defense for this, 1) paypal, you can always email paypal and tell them what happened, you got screwed, the person refuses to give you your money back, and they will be happy to credit the money back to your credit card or bank account. or 2)your credit card company/bank, just tell them what happened also and that you got screwed and they will be happy also to credit the money back to your credit card, or bank account. so, one of the two ways, you'll get your money back from someone that may decide to screw you, they may get away with stealing your money and screwing you, but you'll get YOUR money back from either paypal or your cc company/bank.