Virtual directory is logical linked between physical directory and webserver, All virtual directories are located in the webserver memory, All physical directories are located in the server machine memory, Using one virtual directory we can communicate with only one physical directory.
Creating Virtual directory
Create physical directory named with "yahoo" Right click on the yahoo folder click on properties select web sharing tab. select this folder radio button.
Alias name="my yahoo" -----> OK, created
When we are installing IIS web server Automatically created folder in the administrative tools named with internet information services, All virtual directories are located in the IIS folder.