[Exim] simple standalone novice config

I'm trying to configure a stand-alone Debian box connected by modem
to a commercial ISP so that fetchmail will collect. exim act as MTA and
Pine as reader and email preparer etc. My ISP uses 'pop' for mail server,
'relay' for SMTP and 'news' for NNTP.

At the moment, I'm confused by a number of things. Much of my first
attempts must be OK for I can send email (using Pine) and collect
(via Fetchmail - although it justs dumps everything into /var/spool/
mail/<username>). Basically, things are messy and I seem unable to
grasp the fundamentals of the overall picture.

Hypothetically, my system is 'eden', only user is 'adam' (there may
eventually be a second, 'eve'), ISP is 'ark.co.uk' where I log in as
'noah' and use as password 'dove'.

In the basic configuration of exim, the second question asks for 'the
'visible name' of your system'. That suggests 'eden' - however, I have
a beginners guide which says 'set the visible name to the name of your
ISP'. Most other literature (of which I have too much!) does not define
what visible name means nor from where it is viewed. The same guide
says 'set smart host to the SMTP server' which seems clear and logical.

I largely understand the role of 'postmaster', but it appears to cause
confusion if I adopt some of the suggestions I've read. It seems I
understand more of the complex requirements for large networks since
most of what is written relates to these and very little of the needs of
simple sysems like mine.

Can anyone suggest a source of a simple explanation and definition
of words and expressions used so that I can get some overall
understanding of mail. If I am right, some words have different meanings
according to circumstances.

Regards, John.