What does "Restart Style" mean in Session and Startup (and how does one change it)?

[Chris Green]

In the "Session and Startup" "Session" tab xfce shows the current
session processes that will be saved by saving the session (and thus
will get restarted on reboot).

I have a number of questions about this but the most pressing one at
the moment is what does "Restart Style" actually mean and how do you
change it.  In particular what does "If running" mean in the column?

Also what determines whether a program will appear in the list or not?
I'm running some programs (Firefox, Thunderbird in the panel, a game)
which don't appear but everything else I'm running (thunar, virtualbox
and various xfce utilities) do appear.


-- 
Chris Green