[Zope] .dtml files

I've been digging into to the inner workings of Zope trying to gleen as much Zen as possible, before I implement a write of our existing framework. During this process I have noticed that Zope's dtml pages are stored on the file system as .dtml files (i.e. roleEdit.dtml) The question then is how does Zope display this pages?? I have found function calls such as: manage_roleForm=HTMLFile('roleEdit', globals()) which I believe creates an HTML document template from the named file. But, what is the mechanism that calls/displays mange_roleForm? Thanks in advance, DR