For the record, X-Terminal is just an interface - the commands you use through X-Terminal aren't part of X-Terminal, they're just command-line programs available on the system. Most of the basic ones are built in to the "busybox" binary, which is a configurable package that includes (or can include - which ones are included is determined when the binary is compiled) within it a large number of command-line tools common in linux systems. I suspect that as the N9 gets more attention and more time passes, developers might start providing command-line utilities for installing, which would then hopefully let you use them from X-Terminal.

cddiede, "start" and "stop" are commands for job control - I'm not too experienced in this myself, but "jobs" are basically a way for you to have shell commands working in the background while doing something else in the foreground without having to open more than one X-Terminal window. For example, if you're using the x-terminal editor vi to edit a text file, but then want to run some other command, pressing Ctrl+Z would background the vi editor, and you would get the shell back - the editor would still be running in the "background" of that X-Terminal though. 'start' and 'stop' let you initiate and terminate jobs with more control, in other words.

- Edit -

Since I never used start/stop commands myself before, and only started learning them to answer cddiede's question, I want to point out that my information isn't guaranteed to be completely accurate.

Anyway, start/stop commands are symlinked on the N900 to "initctl" - do you have that command on the N9?