The Windows Subsystem for Linux (WSL) is a way of running a Linux distribution efficiently as your own user, on Windows. (No dual-boot or Virtual Machine (VM) needed. It seems to be more like a container?)
While WSL1 seemed to “just” emulate the Linux syscalls on a Windows NT kernel (so there specifically was no “Linux” running at all), WSL2 seems to “fix” this by running a full-blown Linux kernel .. alongside Windows, via its own Hyper-V hypervisor.