Microsoft has made major changes to the way that they build and release their operating systems. The new Windows Server “Semi-Annual Channel” (SAC) marks a substantial departure from the familiar release pattern that Microsoft has established. The change has pleased some people, upset many, and confused even more. With all the flash of new features, it’s easy to miss the finer points — specifically, how you, your organization, and your issues fit into the new model.
More details can be read on this highly informational article by Altaro: https://www.altaro.com/hyper-v/windows-server-semi-annual-channel/