Parallels Folder Sharing: Which Protocol?

Hello,
my Mac OS drive and other location on MacOS are accessible in Windows Explorer as Network drives.
Could somebody please tell me what protocol is used to access these drives?
Or is this just the normal way that any MacOS programm accesses files on the harddrive where it's installed, and Parallels then transforms this into "virtual" network drives readable by the VM?

Thanks

 

SMB