https://arstechnica.com/information-technology/2019/07/microsoft-changes-windows-10s-update-model/

Microsoft outlined new directions for Windows 10's update model in a pair of blog posts. It looks like the company is shifting its twice-annual major release cycle to a twice-annual major/minor release cycle, with major upgrades in spring and minor upgrades in the fall.

To understand the shift, you need to know a little about how Microsoft has released Windows 10 builds to date—and particularly, how they've released them to Windows Insiders. In short, Fast Ring subscribers are the first to get new features and updates. Slow Ring subscribers get those features before they're public but not until after the Fast Ring folks have had a while to flush out the worst of the bugs.