The WORLD System, acronym meaning "Ways Of Reordering Life's Destiny", and also referred as World Tarot, is a gameplay mechanic introduced in the PSP version of Tactics Ogre: Let Us Cling Together.
The WORLD is unlocked after the game is finished the first time. Like the CHARIOT, it works differently from other tarot cards. Unlike the CHARIOT, it can only be used outside of battle to travel to another point in the story.
When obtaining the WORLD for the first time, the only route and events unlocked will be those you have already done, but from those you can travel to different points in the story and experiment to see what happens if you took certain choices.
Anchor Points, which are what you use to travel to the points in the story, will not be overwritten unless you play to and past them again, which is when they will take on the new events. For example: Since Chapter 4 is shared between all of the routes, if you completed Chapter 4 on Chaos route first, then went to Chapter 3 Law and then beat Chapter 4 on Law will make the entire Chapter and CODA be aligned with the Law route's events instead of Chaos.