Theme pages

If wrong place to post, forgive...

I'm still trying to fully understand the templating system for Xaraya, 
and am having difficulty with theme pages.

Pages are "Master Templates" as I understand the BlockLayout specs.
All the currently shipped themes have a default page (default.pnt, or I 
guess .xt in the future?),
and the SeaBreaze theme has an additional install.pnt page.  

But how does xaraya know when to utilize a different page?
Is this related to modules?
There is no "install" module, but an "installer" module.

Related to realms, perhaps?
Anyone getting multiple pages to work?

Thanks in advance,
rivanna