I’m a complete beginner learning Python. I noticed the Windows installer for Python states “does not include source” and below it there’s an option to install the source via tarball.
What is left out if I install it with the windows installer without the source?
The source code.
This can be useful as a reference, or if, for example, you are doing Cython development (where you need the source to compile against).
In general though, the source isn’t needed for the average Python user. If you need it, you’ll know about it.