[Zope] Some newbie questions

[Adam Clark]

I think what I really need is a reference:

What can you do with REQUEST? RESPONSE? AUTHORIZED_USER?

It looks like when you say <dtml-var "something"> it's plain
Python.  What's the context?  What do I need to do to call some function
in a product class?  What about a function in a class under some other
folder (ie. corresponding to some arbitrary URL)?

From a product class function, is there a way to do a server redirect?

What should I use for managing users (seems to be GUF, LoginManager, maybe
others)?  How about a threaded message board?  There seem to be a number
of products planning not to continue from their current codebase.

Can anyone explain ZClasses?  Where's all the code?  Is that the future of
Zope?

Just hoping to find the road.  Thanks a lot!

Adam