A terminal emulator, A terminal emulator is a computer program that emulates a video terminal within some other display architecture (for example in a DesktopEnvironment). It allows interacting with CommandLineInterface programs.
Here are some terminal emulators available in Debian repositories:
gnome-terminal a terminal for GNOME
xfce4-terminal a terminal for Xfce
eterm a terminal for Enlightenment
xterm a basic terminal for the XWindowSystem