Basics

A Free and Open Source word processing and office/productivity software suite
Can essentially be a direct substitute for things like Microsoft Word or Google Docs (outside of available fonts, and cloud editing mainly, see the section on this)
Technically speaking is LibreOffice, but for convience sake feel free to use Libre Office

Scripting

It's possible to remotely control LibreOffice via python using the python Uno bridge. See How much interest is there to integrate LibreOffice into FreeCAD? FreeCAD forum thread for more details.