We'll be brief this time around.
We were verbose in our first introduction of this feature back in 2012 and that didn't help anyone. To read our original introduction please read this pull request title and first comment: https://github.com/ezsystems/ezpublish-legacy/pull/284#issue-2929770
In short: eZ Publish layout/set module view has lacked view parameter support.
It lacks this support even though the layout/set module view can be used to view existing module views and templates which already expect view parameter support as provided by the content module.
This creates serious template variable conflicts for existing content view templates.
Our simple code improvement brings in layman's terms view parameter support to the layout module indirectly.
It does this by providing view parameters to other module views which make use of eZModule:STATUS_RERUN requests ie: custom modules or modified copies of the layout module in extensions.
Thank you for your continued support!