Does anyone know the difference between when a fragment of papyrus will run for an AI package?

On Change is pretty simple. On Start is pretty simple, too.

But when would On End run for a sandbox package that requires the NPC to travel a distance?

Would it be after they arrive at the new sandbox location, or after they arrive AND the sandbox routine completes (which effectively makes it about the same as On Change)?

Thanks!

On a travel package, on end would probably mean when the npc arrives at destination. You should have asked there: http://www.gamesas.com/topic/1480911-quick-questions-quick-answers-thread-30/?p=23226960