|e / edit||tells Maya you want to change the value of an existing property|
|q / query||tells Maya you want to get the value of an existing property|
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.