TextEdit is described as 'When you need to create text documents, TextEdit is a highly versatile word processor, including tools to format and layout your page, edit and stylize text, check spelling, create tables and lists, import graphics, work with HTML, and even add music and movie files' and is a Text Editor in the office & productivity category. There are more than 100 alternatives to TextEdit for a variety of platforms, including Windows, Mac, Linux, BSD and Web-based apps. The best TextEdit alternative is Sublime Text, which is free. Other great apps like TextEdit are gedit, GNU nano, TextMate and CudaText.
Nano is a great terminal based editor, but anyone looking for an alternative to TextEdit is of course expecting a GUI application.