Microsoft has announced that they will stop providing security & quality updates to PCs running Windows 10 version 1809 after December 8th 2020.
Support for Windows 10 version 1809 (which came out in October 2018) was due to end early this year, however it was delayed to COVID-19 giving more time to users and IT professional to update their systems. As a result, users with Windows 10 Home or Pro editions of Windows 10 version 1809 will not receive monthly security and quality updates containing protection from the latest security threats after December 8th.
To check what version of Windows 10 you are running, you can open Settings > System > About, and you will see the version number in the Windows Specifications section.
To update to latest Windows 10 Version you can go to Settings > Update & Security > Windows Update.
The version numbers since 1809 have been 1903, 1909, 2004 and the most recent (current) version 20H2.