A Virtual Directory is a virtual folder that points to a physical folder within your site's directory structure... the physical folder may or may not be the same name as the virtual folder, either is allowed.  

Most folks do not have a need for virtual directories except for the fact that a key IIS function is also included in this area, the ability to also set that virtual directory as an IIS Application. 

The following provides instructions on how to create a Virtual Directoy and to set it as an IIS Application, depending on your Plesk version. 

Before you begin, you should know what you want the virtual directory name to be, and what physical directory you want it to point to.  If you are doing this only to be able to set a folder as an IIS Application (the most common reason), then you should have both be the same... i.e., you're creating a virtual folder named "somefolder" that points to a physical folder of the same name "somefolder".   

PLESK 8.x and 7.x

To create a virtual directory in PLESK, do the following:

• Log into PLESK at https://webXX.3essentials.com:8443 Where XX is your server's number. (Ex:  WEB24)
• Click on the domain you wish to create the Virtual Directory for.
• Click "Web Directories"
• Click "Add New Virtual Directory"
• Enter the name for the Virtual directory (Ex. if you are setting up a virtual directory named www.yoursite.com/Blog, the name should be Blog.)
• Path: If you have not yet created the folder for the Virtual Directory, keep this box checked, otherwise uncheck it and find the folder.
• Everything else should be fine by default, click OK to create the virtual directory.

PLESK 9.x

To create a virtual directory in PLESK, do the following:

• Log into PLESK at https://webXX.3essentials.com:8443 Where XX is your server's number. (Ex:  WEB26)
• Click on the domain you wish to create the Virtual Directory for.
• Click "Virtual Directories"
• Click "Create New Virtual Directory"
• Enter the name for the Virtual directory (Ex. if you are setting up a virtual directory named www.yoursite.com/Blog, the name should be Blog.)
• Path: 
  • If the physical folder doesn't exist yet, and you want plesk to create it with the same name as the virtual folder you're creating, then SELECT the checkbox for Create physical directory with the same name as virtual directory. 
  • If the physical folder does already exist, then uncheck that box, and use the path field to specify the name of the existing folder.  You can also click the folder icon next to it to browser your site folders to find the existing physical folder. 
• ​If you need the Virtual Directory to also be an IIS application, check the box for Create Application, leaving the Execute Permissions set to scripts only.  
• Everything else should be fine by default, click OK to create the virtual directory.