They're rather complicated. They also include Layer Sets (a feature you can only create with the pro version of Photoshop), have very strict naming conventions and must be layered in a certain order.
But if you're interested, you can find a detailed chapter on creating your own DVD templates using and existing one as a model in my combined Photoshop Elements/Premiere Elements book.
When will the combo book be available. Will it be available in an eBook format?