Why does CORS swear if the address is the same?

Question

CORS

Access to XMLHttpRequest at 'http://pfe.com/public/cabinet/transactions/get' from origin 'http://www.pfe.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

Why does CORS swear if the same address is ` http://pfe.com`?

Answer 1

www, despite its prevalence, in terms of domain naming is no different from abc.
I think it's obvious that the request from abc.pfe.comto pfe.comis CORS.