Web Design in a Nutshell, 3rd Edition

Web root directory

When a browser requests a document, the server locates the document, starting with the server’s root directory. This is the directory that has been configured to contain all documents intended to be shared via the Web. The root directory does not necessarily appear in the URL that points to the document, so it is important to know what your root directory is when uploading your files.

For example, if the root directory on http://example.com is /users/httpd/www/ and a browser makes a request for http://www.example.com/super/cool.html, the server actually retrieves /users/httpd/www/super/cool.html. This, of course, is invisible to the user.