If you are using Windows 10, Version 1803 You will Soon see " You're currently running a version of windows that's nearing the end of support. We recommend you update to the most recent version of Windows 10 now to get the latest features and security improvements" Message everywhere especially in Windows update section of Settings App.
This is because Microsoft, wants all its users to use the latest version of Windows 10, Version 1903, which still has bugs like display driver issue, Bluetooth connectivity issue, sandbox issue, and more issues that are discovered everyday.
So, you can ask do i need to upgrade to Windows 10, 1903? I would say Ya, you can upgrade to Windows 10 May 2019 update, as it contains more features like light theme.
When is Windows 10, Version 1803 Support ending date?
But, you have time, wait for Microsoft to fix the bugs, because the Official support is ending only on November 12,2019 meaning you will still get support till that time..
So, Just ignore the message and Enjoy this stable edition (1809 is the bugful edition, bugs are being discovered even today, so skip it and install 1903 which is safe compared to 1809)