The support for Windows 10 version 1803 (April 2018 update) will end in a few weeks. Microsoft has already begun recommending an update to end-users, before the forced update begins.
If you still use Windows 10 in version 1803, aka Redstone 4 aka April 2018 Update, you will receive a warning message that points to the upcoming support end of this version of Windows. Users can still use Windows 10 1803 until November 12, 2019 - after that, there will be no updates new for this release. Microsoft itself began updating existing systems with version 1803 last July but informs users with message explicitly about the end of support for Redstone 4. Windows users will have to make do with a forced update after the end of the support phase. The notification is:
The Windows 10 April 2018 Update will end on November 12, 2019 for the Home and Pro editions. Beginning on July 16, 2019, we will begin updating devices with the Windows 10 April 2018 Update to ensure that these devices are in a maintained and safe condition
As soon as support for version 1803 of Windows 10 ends, a forced update to the current Windows version 1903 takes place. If you run Windows 10 1809, that will get supported until May 2020.
BTW: to check your version of windows real fast, click on the windows button and type: "winver".