I am not even sure how to explain this properly, but here goes:
Let us say that at IP address xx.xx.xx.xx is a folder called "domainname.com" which itself contains the index.php home page for a site.
Typing http://xx.xx.xx.xx into a browser loads the index.php within "domainname.com" folder.
There is a second folder at the top level called "anotherdomainname.com" which contains a different index.php, for a different site.
What would I type into a browser to view the index.php of this other folder?!
What is telling http://xx.xx.xx.xx that the index.php of the particular folder is what is should load? I have even placed a dummy index.html page at the top level, but it is ignored.