I think that is the structure to create a lot of different GUI application.
The start screen is full of custom push button (like the Iphone) pushing on them you could go to a specific page where you could go to another page/pages pushing other push button.
So it is easy to have 30 pages.
Obviously only 5-6 pages are often used and the other pages less.
Every page has a lot of custom widget to create a personalized GUI application.
I think that is important to understand the best way to do.