Matrix Feature: "Axis whose values change dynamically"

On Kohsuke's slides from the recent user conference ( http://www.slideshare.net/kohsuke/jenkins-user-conference-2012-san-francisco ) there's an item on slide 21 regarding a Multi-configuration Project Improvement: "Axis whose values change dynamically" Can anyone describe what that is and how

Re: Displaying user in the Build History column on the left

I use the Groovy Postbuild Plugin to do this. You can display custom icons in the Build History, too.