Taken from the RealmCrafter: Standard documentation.

Instanced Zones is a new feature as of 108 to Realm Crafter and for those who are unfamiliar with what instancing does or actually what it is, simply instancing is a zone (any zone) that is a copy of an original zone. This is for single groups and guilds to adventure alone or to control population in a zone so that the zone never becomes too laggy or over populated and unplayable.

To use instanced zones you should be very familiar with the Realm Crafter scripting language.  This is important because you must script when the zone is created, and when you use them.

There are new instanced scripting commands as well that will help with this. 

In-Game Commands Edit

In-game Commands.rcscript and Startup.rcscript are the example scripts you would replace your scripts with in your project, they show an example of how to create a instanced zone.

These two scripts do the following: 1. They create an instance of the darklands area. and 2. They allow you to type: /transfera or /transferb to switch between instances while in game.