what does the preview path field do?

https://snipboard.io/2FHjcn.jpg

After I install and enable this module and go to the THEME settings, I see a field called Preview Path, and I don't know what its for or how to use it, and I can't seem to find any documentation on this.

http://ca.ios.ba/files/drupal/csseditor.ogv

This is supposed to be a video link of how to use this module, but that link is not working either.

Please help me somebody.

Thank you.