The UNIX operating system was originally designed as a text-only system, controlled by commands entered with a keyboard. This is known as a command-line interface (CLI). The X Window System, Xfce, and other projects have since added a graphical user interface to UNIX, that's what you are actually using now. But the addition of a graphical user interface doesn't mean that the CLI is dead. The CLI is still around and is frequently the easiest, fastest, and most powerful way to perform a certain task. In fact, power users would be lost without the CLI.
Terminal is what is known as an X terminal emulator, often referred to as terminal or shell. It provides an equivalent to the old-fashioned text screen on your desktop, but one which can easily share the screen with other graphical applications. Windows users may already be familiar with the MS-DOS Prompt utility, which has the analogous function of offering a DOS command-line under Windows, though one should note that the UNIX CLI offer far more power and ease of use than does DOS.
Terminal emulates the xterm application developed by the X Consortium. In turn, the xterm application emulates the DEC VT102 terminal and also supports the DEC VT220 escape sequences. An escape sequence is a series of characters that start with the Esc character. Terminal accepts all of the escape sequences that the VT102 and VT220 terminals uses for functions such as positioning the cursor and to clearing the screen.
Terminal's advanced features include a simple configuration interface, the ability to use multiple tabs with terminals within a single window, the possibility to have a pseudo-transparent terminal background, and a compact mode (where both the menubar and the window decorations are hidden) that helps you to save space on your desktop.
The following key features are available:
Besides these key features, Terminal supports all the features you would expect from a modern terminal emulator.