easy_install: Forget it existed, substitute with pip

virtualenv: A virtual environment, providing an isolated Python and libraries

mkvirtualenv: A script to create a virtualenv

pipenv: Combines pip and virtualenv into an integrated solution, comes with a Pipfile not unlike Ruby's Gemfile for example

pyenv: Script that helps to install and manage different Python versions on your system, so you can have the full range of Python 2.x and 3.x installed without them getting in the way of each other. Allows you to set local, default and system Pythons allowing you to switch your Python interpreter depending on which project/directory you're in