This documentation covers coding for Autodesk Maya. It's not meant for end-users of the Maya software. (To find out how to model or animate in Maya, try Autodesk's introductory videos or an end-user site like CGSociety.)
Maya supports 3 programming languages: MEL, its built-in scripting language; C++, which is used for plugins; and Python which is common for integration jobs but can also create plugins using a wrapped version of the C++ API
This page should cover various ways to set up Maya python paths - userSetup, maya.env, environment variables and so on
Maya comes with a fairly complete UI toolkit that includes windows, layouts, and a variety of controls. This is implemented using the QT framework in C++, but exposed to MEL and Python users via the default Maya command set.
Advanced users can extend the Maya UI using either C++ or Python. Maya versions from 2012 to 2016 use Pyside and QT4; Maya 2017 uses Pyside2 and QT5. More details here
Note: Older reference on the web refers to the Maya GUI toolkit as "ELF"; that's still the correct name but it's rarely used.