The state of Python packaging was very confusing for a long time and it took many years to bring organization to this topic. Everything started with the distutils package introduced in 1998, which was later enhanced by setuptools in 2003. These two projects started a long and knotted story of forks, alternative projects, and complete rewrites that tried to (once and for all) fix the Python packaging ecosystem. Unfortunately, most of these attempts never succeeded. The effect was quite the opposite. Each new project that aimed to supersede setuptools or distutils only added to the already huge confusion around packaging tools. Some of such forks were merged back to their ancestors (such as distribute which was a fork of setuptools) but some were left abandoned (such as distutils2).
Fortunately, this state is gradually changing. An organization called the Python Packaging Authority (PyPA) was formed to bring back the order and organization to the packaging ecosystem. The Python Packaging User Guide (https://packaging.python.org), maintained by PyPA, is the authoritative source of information about the latest packaging tools and best practices. Treat that site as the best source of information about packaging and complementary reading for this chapter. This guide also contains a detailed history of changes and new projects related to packaging. So it is worth reading it, even if you already know a bit about packaging, to make sure you still use the proper tools.
Stay away from other popular internet resources, such as The Hitchhiker's Guide to Packaging. It is old, not maintained, and mostly obsolete. It may be interesting only for historical reasons, and the Python Packaging User Guide is in fact a fork of this old resource.
Let's take a look at the effect of PyPA on Python packaging.