What is the Macintosh HD.hdd for?

[MacCentris]

All right so, I installed Mojave as a guest OS in an external USB (for travel purposes and such) and at the end I have the virtual machine AND a .hdd file, I don't see such thing for the Windows machines, the .hdd file takes almost 6 GB which is not that big of a deal, but is that part of the installation, can I now get rid of it? I appreciate everyone's help, I'm still quite new to Parallels

Liliana

 

[Mark Fine]

I don't see such thing for the Windows machines, the .hdd file takes almost 6 GB which is not that big of a deal, but is that part of the installation, can I now get rid of it?

Think that's at least part of the virtual hard disk for the VM (given the size, possibly a recovery partition?). You do not want to delete that.
Your Windows VMs have an .hdd file as well but are within the .pvm itself.