Microsoft if you're reading this this is your fault for not marketing enough.
WSL is windows subsystem for Linux. Think of it like this- say you have an 'ls' binary from UNIX machine. You have WSL enabled on your machine in Windows. Windows will start the ls process and the UNIX calls will be handles in windows. (the kernel has mappings).
It's possible, and actually its wonderful experience, to run full "linux" environment right from windows at native speed.
It's not perfect and one of the biggest issues has been file system speed but besides that and some other smaller issues its the absolute best of both worlds- OneNote + excel + outlook + i3
