https://wccftech.com/march-2019-windows-10-cumulative-updates-are-out/

Microsoft has started to release Windows 10 cumulative updates for this month, pushing out a number of bug fixes and improvements. Today’s updates are so far only available for Windows 10 April 2018 Update (version 1803), but we expect to see patches arriving for more versions later today.

The Windows maker wrote that today’s update is one of the last two Delta updates for Windows 10 1803. “Security and quality updates will continue to be available via the express and full cumulative update packages,” the company wrote. Delta updates are usually larger than the express updates that deliver only the updates that are needed, and not the entire packages. You can read more about delta, express, and full updates in this blog post.