Broadly speaking WSL1 is linux implemented in the windows kernel, think reverse wine. WSL2 is linux running on a thin VM with several bridge layers that can access windows resources (networking, files, GPU, etc.)

Isn't WSL1 everything _but_ linux? I.e. more like gnu/WinNT.

Thanks for the explanation! I always knew that WSL1 was implemented on the Windows kernel and thought it was quite ambitious - props to them! I didn't know they moved to the VM model for WSL2.

Everything, WSL2 is a special hyperv vm. It’s a true Linux kernel with a true Linux file system. The network stack is one way integrated so you don’t have to forward any ports or configure NAT.

WSL2 uses VM. So actual Ubuntu distribution under the hood

It runs a hyper-v VM with a Linux kernel.