What does "pyenv virtualenvwrapper" do?

Question

I am using pyenv with virtualenvwrapper.

For using virtualenvwrapper (without pyenv) I have in my .bash_profile source /usr/local/bin/virtualenvwrapper.sh

When using pyenv with virtualenvwrapper plugin what exactly does pyenv virtualenvwrapper do ?

What I see online is this is required to setup a virtualenvwrapper into your shell . Is it still required if I have sourced virtualenvwrapper.sh ?

To add some more details: as per https://alysivji.github.io/setting-up-pyenv-virtualenvwrapper.html

Anytime we install a new version of Python, we will need to install 
virtualenvwrapper. This is done with either the pyenv 
virtualenvwrapper or pyenv virtualenvwrapper_lazy

Is it required only once when a new version of python is installed in pyenv ?

Answer 1

In short, from the pyenv-virtualenvwrapper readme :

pyenv-virtualenvwrapper is a pyenv plugin which provides a pyenv virtualenvwrapper command to manage your virtualenvs with virtualenvwrapper.

There are three tools involved here:

1. virtualenv or venv - Used for isolating python environments (collections of packages) by using 'virtual environments'. virtualenv has been more or less superseded by venv , but for the purpose of this answer, they are interchangeable.
2. virtualenvwrapper - A set of tools for automating some of the steps involved in using virtualenv or venv .
3. pyenv-virtualenvwrapper is a plugin that allows virtualenvwrapper to work with pyenv
4. pyenv - a tool for managing multiple versions of python on the same computer system.

Another way to manage virtual environments when using pyenv is pyenv-virtualenv