https://arstechnica.com/gadgets/2019/02/latest-windows-preview-build-skips-all-the-way-to-a-2020-release/

Microsoft has published a new preview release of Windows 10, build 18836, to participants of the "Skip Ahead" group. But it's not quite the preview that they were expecting to get.

Microsoft's preview program has a number of different channels to let people use and test Windows feature updates, Microsoft's twice-yearly Windows 10 upgrades. The two main channels are Fast and Slow; Fast receives builds more regularly, while Slow generally receives only those builds that are felt to be stable. Both channels look ahead to the next feature update. For example, right now, the stable Windows 10 version is 1809. The Fast and Slow channels are receiving previews of version 1903, codenamed 19H1, which is due for release in April.