TLDR: Run Windows userland apps from Ubuntu bash with Linux --> Windows path correction
Microsoft ships the Linux Subsytem for Windows, which is an Ubuntu userland running native ELF binaries. It's not a VM, it's not Cygwin, the processes are legitimate Windows processes running through a compatibility layer.
You can also run native Windows apps from the shell. Yes, it's ok to run
/mnt/c/Windows/System32/notepad.exe and it works! Ok, so what's the catch? Say
you want to open a file with notepad like this
/mnt/c/Windows/System32/nodepad.exe /mnt/c/users/rob/Documents/goodstuff.txt.
In Windows userland, /mnt/c/.... doesn't mean anything. That is what these
shims are for. Using Powershell for Linux, we convert the Linux virtual path for
a file to the actual Windows path. This way
notepad ./goodstuff.txt becomes notepad C:\Users\Rob\Docu,ents\goodstuff.txt