It is a crazy way to connect the x120 (when running MS Windows) to a PC running MS Windows. It is partly explained in the online manual that came preloaded on the x120.
To my Linux PC, the x120 looks like a little mass-storage device holding some auto-install MS Windows software (i.e. useless). I presume that if my PC were running MS Windows, the software would install and know how to share files across the USB wire. Yuck.