I learned about the pstree command in the book 'Linux System
Administration' by Carasik (ISBN:0764570080).

You can learn a ton about this command viewing the manpage (type: man
pstree).  I also went into depth as to what's in my process tree.
Click Here to view my discussion about the process tree that the pstree displays.

Also, below is the process tree that showed up when I typed pstree
at the command line on my Digital Starion 910 desktop running debian, X,
and the blackbox Window Manager.

neonprimetime@sandra~$: pstree
init-+-anacron
     |-atd
     |-cron
     |-diald
     |-6*[getty]
     |-inetd
     |-keventd
     |-kflushd
     |-klogd
     |-kswapd
     |-kupdate
     |-lpd
     |-portmap
     |-rpc.statd
     |-sshd
     |-syslogd
     |-xconsole
     |-xdm-+-XF86_S3
     |     `-xdm---x-window-manage-+-ssh-agent
     |                             `-xterm---bash---pstree
     `-xfs