"how to call the container for the libraries, the one thing providing the environment?"

In Visual Studio we call these Environments (in the source they're still referred to as Interpreters). A "virtual environment" is just a specific type of environment (one that inherits a stdlib and/or packages), as is an isolated environment (hosted in an app, or a conda env). They all specify a Python version and concrete versions of libraries - something directly executable, not something that needs to be actualised before use.

Not sure that we need an official term, but the venv docs likely have or need a definition to work with.

Cheers,
Steve

Top-posted from my Windows Phone