We presume a non-WYSIWYG approach to text processing: that you need to issue explicit command in your file. E.g., if you want to center a title, you need to type in your file a command to center it.
In contrast, a program like Microsoft's Word, tries to combine the functionalities of a text editor with that of the text processor.
Most Unix users prefer TeX or LaTeX for preparing their documents. Especially for mathematical typography, this is unequalled.