Newbie hacking question

Fairly naive, but trying to make some minor changes in my (happily) working
RT system (2.0.13 - using postgress/Linux)

Where is the $session stuff set up? I’m trying to play with some of the
defaults that are set in any new sessions that are created during web
interactions - does this live somewhere (hidden) in RT or an outside
module. The variables obviously map mostly into real RT values but are
there others I should be able to get to also?

Any pointers appreciated.