"WSL 2 is a new version of the architecture that powers the Windows Subsystem for Linux to run ELF64 Linux binaries on Windows," Microsoft writes in the announcement blog. "This new architecture changes how these Linux binaries interact with Windows and your computer’s hardware, but still provides the same user experience as in WSL 1 (the current widely available version). Individual Linux distros can be run either as a WSL 1 distro, or as a WSL 2 distro, can be upgraded or downgraded at any time, and you can run WSL 1 and WSL 2 distros side by side."
One of the key differences between WSL 1 and WSL 2 is the introduction of a real Linux kernel; one that Microsoft is tuning specifically for WSL 2 and developing in house based on the latest stable branch. The initial offering will be based on kernel version 4.19. Microsoft will host its custom kernel on Github and says it will be fully open source (Microsoft is also giving its new version of Terminal the open source treatment).
As someone who never uses Linux I'm not really sure if this is a good thing or not, but it sounds like a positive step in the right direction.
That's correct, this is a step in the right direction. Windows Subsystem for Linux 1 was emulating a Linux kernel. With an actual Linux kernel it will improve filesystem I/O performance, Linux compatibility and actually run docker natively.
They're also using the kernel for Azure Sphere and hopefully not in the too far distant future a Windows Linux based desktop OS.
Microsoft's only reason for this is to increase Windows 10's user numbers by getting Linux users and dual booters, mainly developers, to switch to Windows full time, which gives the impression that Linux's market share is higher or gaining faster than people realize for MS to spend the effort.
I don't think this is to entice Linux desktop users in order to improve Windows 10's user numbers. Even if they got them all, and they wouldn't, it would not be a significant bump. I think it is to make life easier for developers. They are already using embedded Linux everywhere and they need to test their code. Not needing a separate test box makes this easier and Microsoft really wants to keep providing developer boxes. Also, services based on open source software is a great business model which even Microsoft is starting to believe in, so making open source development easier is important for them too.