What is the difference between developer.paypal.com and x.com?

Question

I thought that I have a developer account at PayPal (still logging in successfully to https://developer.paypal.com), but when clicked the PayPal Developer Network link on that page (to ask a question that's specific to PayPal API), I was prompted to login again. This time, my developer.paypal.com's account userid & password simply wouldn't work there.

Am I supposed to create another account there? If so, will it be linked to the developer.paypal.com one (just as accounts in SO/SE are linked)?

If I may explain my confusion further: I have a "regular" PayPal account (for purchasing stuff online), I have a business account (for accepting online payments), I have a developer account (for testing integration of shopping cart with paypal). How many accounts do I need with PayPal? When I create an x.com account, will it conflict with my existing accounts?

Thanks.

EDIT: What's even more confusing is the question in the login page to x.com:

Already have a PayPal account?

Well, of course I have a PayPal account. In fact, I have 3 of them. Do I need to create another one, just to post a question in the developer network forum?