Okay, your first mistake is consigning yourself to newbie-land
Slackware 12 is not too much for a newbie; how else are you going to
learn? Slackware is an excellent distro with plenty of
beginner-friendly documentation (Slackbook), so dive in!
As far as understanding users: you're always logged in under the
user you logged in as, however there are processes and devices that
are run under different users. This is a groups (as in /etc/group)
issue; add yourself to video, cdrom, plugdev and a few other groups
I have had a lot of success just entering the exact error message into
Google and seeing what I come up with.