Yours isn't either! You do not even mention a single answer to the above question!

BASIC:
x-terminal is a program to display the command-line-interface (also referenced to as CLI or text-shell) in a GUI (graphical-user-interface) environment (thats the desktop you see and can click on).

DETAIL:
A shell is actually providing an interface to the system.
A shell providing a text-interface (ash, bash, ksh, ...) is called CLI and providing a graphical-interface (windows explorer, kde, gnome, ...) is called GUI.

In N900's case the provided text-shell is ash, that can be changed if needed.