Updated 2020/02/18 to reflect changes introduced in WSL2
Hi! Microsoft PM working on WSL & Command Line here.
WSL allows you to run native, unmodified Linux ELF-64 binaries directly on Windows, and enables you to run your favorite Linux tools atop your Windows "host" OS.
WSL1 took an approach of adding a Linux syscall compatible layer at the top of the NT kernel, allowing Linux binaries to run atop NT, sharing the same underlying filesystem, networking, process list, etc. as the host OS.
The soon to be released WSL2, on the other hand, runs distros' binaries within Linux containers, atop a real Linux kernel, inside a lightweight VM that allocates only the RAM needed by the apps it runs, and then releases freed RAM back to the host OS. This provides 100% Linux compatibility, and allows your Linux tools to run with near native performance, and consumes minimum resources necessary from the host, ensuring your machine runs fast and smoothly.
Prior to WSL2, one could run the Docker client in WSL1, using it to drive Docker for Windows running atop Hyper-V on the local host, or to manage a remote Docker server. But one cannot run Docker Engine on WSL1 for many technical reasons.
However, you can do the same in Docker on WSL2, but you can also run the Docker Engine itself atop WSL if you prefer. This is, Docker's preferred and future path for running Docker on Windows desktop.
To learn more about WSL, review the videos & docs here: https://aka.ms/learnwsl