The term always seemed self explanatory, but I just realized I have no idea what Shading Domains are all about.  I guess I have three basic questions...

What defines a shading domain?  Is it unique to an object or some way of keeping calculations for one shader from affecting another?

Is it something I need to understand?  Are shading domains a form of scene optimization, or something that allows you to create specific materials?

Is this something unique to Carrara, or perhaps called by another name in other programs?