Matrix Feature: "Axis whose values change dynamically"

[Ken Bertelson]

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 that works?

I think that I really want that!

Thanks.

Ken B.