WebDav in this context is a tool that turns a folder in your Microsoft file manager, into your Harbor site. So for example if you drag a new application into the folder on your PC, no matter where your Harbor site actually is, it will be installed there as well. 
Nice if your Harbor is hosted on a remote SP.

In response to many requests, this is now packaged with Harbor, so it works out of the box. Please refer to the notes in Harbors web.xml file for fine tuning.