Python modules "Processing", "Multiprocessing" and other concurrency modules: what are the differences?

I am starting to read up over possible ways to parallelise Python code.

DISCLAIMER. This is NOT a question about Multiprocessing vs Multithreading.

At this link https://ipyparallel.readthedocs.io/en/latest/demos.html one finds references to several concurrency packages for Python to avoid the GIL: https://scipy.github.io/old-wiki/pages/ParallelProgramming

-IPython1

-mpi4py

-parallel python

-Numba

There is also a multiprocessing package: https://docs.python.org/3/library/multiprocessing.html

And another one called processing: https://pypi.org/project/processing/

First of all, it is not at all clear to me the difference between the latter two above; what is the difference in using between the multiprocessing module and the processing module?.

In general, I fail to understand the differences between those all -- which must be there, given some developers made the effort to create a mpi4py version for the MPI used in C++. I guess this is not just about the dualism between "threading" and "multiprocessing" approaches, where in one case the memory is shared while the other has each process with its own memory and interpreter, something more must be different between all of those different packages out there.

Thanks to all of those who will dedicate time to answer this!

from Python modules "Processing", "Multiprocessing" and other concurrency modules: what are the differences?