wordpress site name by url query string

If you own the domains, and their name servers are pointed to your hosting place’s name servers, then you can add each domain (via hosting process) and point it to the same folder.

That should allow example.com and domain.com to have the same content, while retaining the domains in the address bar.

You might have problems with image URLs, though, so you might need a few htaccess commands to fix that.