Python 3 versions

[Jose Isaias Cabrera]

Greetings.

I am going to start a project using python, but I need to be able to run some of the python3 libraries. When I use setup to install python, there are a bunch of python* versions:
python2*
python3
python36*
...
python39*

I know that python2 is, probably, on its way out. But, why so many choices for versions of python? One more question, if I install python3, does that mean that I can use all of those python3x libraries? In other words, can I use the libraries of python37* or python38* or python39? Or are these specific to those versions? Confusing, it is. Thanks.

josé