Well, the answer to your question is actually yes and no.
Why? Because as far as I am aware, to have 'PayPal money' in your PayPal account, you need a bank account to be linked to your PayPal account (Unless someone sends you money).
So when you go to buy a domain for example, you are correct in that you do not need to enter any banking details to complete the PayPal transaction. You just:
- Go to the checkout page on the domain registrar's website, select PayPal as your payment method
- Enter your PayPal username and password and login
- Then PayPal will tell you it is deducting the money to pay for the domain from your PayPal balance - this is your 'PayPal money'.
- Simple as that.