Actually, saying that Emacs is a text editor is somewhat misleading; it's also a... Lisp interpreter Virtual machine Compiler Debugger Mail client News reader GUI toolkit Documentation viewer Calendar Window manager Terminal multiplexer IRC client File manager XML parser Tetris implementation Wiki Diff/Merge tool Typesetting system vi emulator Spreadsheet Conversation partner Version Control interface Socio-political statement And with third-party libraries can become... Package manager Collaborative editor Web server Jabber client Blog editor Video editor Typing tutor Web browser IRC bot Twitter client Feed reader