Xrefing refers to the capability of RENDERLights to import models without modifying the original file.
You can xref many files and different formats in to one single scene.
Xrefed files can be turned on and off in order to reveal parts of you models or different variations.
Binding xrefed models will collapse the geometry to the scene, collapsed models will then loose the linked functionality.
Organize your scene by components using xref file linking, Terrain, buildings , cars, people and any other element can be imported as
xrefs, that way you can easily update some components and save time without loosing your work entirely.