Defines in which case a build on the next node should be triggered.
If you choose to disallow multi node selection, the user will get a dropdown with the possible nodes when triggering a build - otherwise a multi selection is possible...

There are different options to define when the next build/job should be triggered: Note: in case of concurrent job execution, the first job will trigger all the other ones, therefore it is important the selected nodes are online - otherwise you risk that none of the jobs will be triggered, because the first is waiting for an executor in the queue.