Clarification wanted on apt upgrade/update and synaptic etc.

[Chris G]

I'm moving (probably) to Ubuntu from Fedora.  I'm installing Ubuntu on
new hardware leaving my Fedora system on the old hardware until I can
rely on the new system.  

I'm a mostly command line person (at work I'm a developer on Sun
Solaris 'legacy' systems), I cut my Linux teeth on Slackware.  Thus I
tend to use the command line in preference to GUI.

I have installed Ubuntu 8.10 beta on my new system knowing that by the
time I have decided to rely on it 8.10 will have been released. I understand
the fundamentals of what apt/synaptic are doing (having used yum/rpm for
a while) but I'm still feeling my way a bit as regards the details of what's
going on. Now on to my questions:-

    What does 'apt-get update' do?  Is it just updating my local copy
    of the distribution lists to the latest versions of available
    software? 

    If I do 'apt-get upgrade' will it do (have done?) an update of the
    file lists automatically?  Is there some sort of algorithm used to
    decide when an 'update' is required?

    When the GUI (from gnome-panel) pops up and tells me that upgrades
    are available is it taking me to the 'same place' as I will get to
    by doing 'apt-get upgrade'?  It seems to take much less time, is
    this because it has already done some of the work in the
    background? 

    If I keep upgrading my 8.10 beta will it become the 8.10 release
    version in due course or do I need to take any special actions to
    achieve this?

-- 
Chris Green