This is how Paypal works now to the best of my understanding
Paypal now links directly to your bank account for Users in Westernized nations. This allows Paypal to directly take funds from your account to pay for purchases.
There are two tiers for paypal users. Verified and non-verified (down from 4 tiers). A verified member has been contacted by paypal and his address/telephone and bank, CC details are confirmed.
If you have a CC and are using Paypal this adds an extra layer of protection as it gives you yet another person you can complain too. If you have a linked CC on your account if your bank is short money they will pull money from your CC.
I prefer to make all purchases via paypal using my CC even if I have a positive balance on my account. Again the reason is because there is an extra layer of protection provided by my CC company.