In a GUI-based word processor you are limited to the choices offered by the menus and buttons in the window, just like driving a car limits you to following the roads. Emacs forces you to climb into an airplane and learn how to use short cut key bindings and automate editing functions, leaving the constraints of a GUI-based environment behind. While it may require some thinking ahead, once you are in the air you can go to your destination much more efficiently.
To get started, find Emacs or XEmacs in the programs menu of your Linux desktop or type in "emacs &" in a shell window. After emacs starts up, press the Esc-key followed by the x-key and type in "help-with-tutorial" and hit return. A tutorial should start up within Emacs that shows you the basics.
One of the strengths of Emacs is the ease with which you can define and use keyboard macros. Whenever you need to perform repetitive operations, for example when systematically editing a table, you can record the sequence of key strokes and replay the sequence a specified number of times with a few quick key strokes.
Emacs recognizes many different file types and uses suitable color coding of the text. For example if you edit an HTML file, the tags will be colored to be easily identifiable and readable.
To exit Emacs type Ctrl-x Ctrl-c. Emacs still comes with most Linux distributions, including all the major distros. Ubuntu users can install it with the Add/Remove function from the Applications menu. By the way, Emacs stands for Editor MACroS and was originally written by Richard Stallman, Guy Steele, and Dave Moon.
The complete documentation can be found here.