The Distortion World is a special dimension that's connected to the real world through specific locations, like the Turnback Cave or the Spear Pillar.
Here's how the Distortion World works:
* Entering: You enter the Distortion World through certain specific locations, and you're automatically teleported out once you've completed the relevant events.
* Exiting: You don't manually choose to leave. The game will automatically take you back to the real world once the events within the Distortion World are finished.
For example:
* Turnback Cave: You enter the Distortion World through this cave, and the only way to leave is to defeat Giratina. Once you defeat Giratina, you are automatically returned to the real world.
* Spear Pillar: You enter the Distortion World at the top of the Spear Pillar, and the only way to leave is to complete the events related to Dialga and Palkia. After you've done this, you'll be teleported back to the real world.
In essence, the Distortion World is a separate dimension that you're only temporarily transported into to progress the story. You don't choose to leave; the game handles the transitions for you.