A python module is a single python file. The module's name is the file name without the extension.
A package is a single python application that consists of modules and subpackages.
An __init__.py file is required in every directory and sub-directory where modules/sub-packages exist for a package. This file is generally empty but may contain code to initialize the package.
The __pycache__ directory caches (saves) "compiled" python code. The timestamp of the python file is checked. If it's been updated, the cache is updated.
Module search path:
/user/local/lib/python/