The GNU Emacs Manual calls Emacs the extensible, customizable, self-documenting real-time display editor, but this description tells beginners little about what Emacs is capable of. To give you an idea, here is a sampling of the things you can do with Emacs:

Beyond just being able to edit plain text files, Emacs includes special features to help you write in many different programming and markup languages:

Similar applications: 
Pico, Nano, VI, VIM, Notepad, Wordpad