This plugin is a power up for the multi configuration jobs allowing you to configure jobs to run on all slaves under a single label.
Ever wanted to have your own personal cloud and use Jenkins a cloud manager, allowing you to create distributed tasks to run over an array of computers? I'm not talking about just running integration tests, I'm talking about real distributed tasks, the sort where the more computers the faster you complete the task.
Another issue addressed by the Elastic Axis is the offline nodes. Sometimes, the computers in your cloud might end up in maintenance or go offline for some reason. With the Elastic Axis, you can check and an option instructing it to skip this these nodes if they are not available, and therefore, you your tasks may take longer, but the job will complete without hanging out because of offline nodes.