Virtual directories and virtual paths are not directly related, the virtual directory is a standalone application, simply said a site if you do not set up a virtual directory, run up is a standalone application, as long as the virtual directory is not established this is always a, set up a virtual directory to add an application.
And many programs require a global variable file that needs to be placed in the application root directory. For example Http://www.xxx.com/BBS this address, if you put in the website home directory of the BBS folder, the global variable file is not available, but you can create a BBS virtual directory, the global file can be placed in the virtual directory is possible The most typical application is the search engine's robotic crawling file. There is a virtual directory convenient, not necessarily put to the site root directory, so can be managed separately, and so much security, you can re-design access rights
Web virtual path