Windows uses dynamic link libraries extensively. DLLs allow collections of functions, usually written in C or C++, to be stored in one file and loaded dynamically by many different programs. DLLs influence everything that happens on Windows; indeed, the Windows API is a collection of such DLLs.
Python is written in ANSI C, and one of its original design goals was to be easy to extend and embed at the C level. Most of its functionality lives in a DLL, so that other programs can import Python at runtime and start using it to execute and evaluate expressions. Python extension modules can also be written in C, C++, or Delphi to add new capabilities to the language that can be imported at runtime.
The Win32 extensions for Python, which we cover throughout this book, are a collection of such libraries that expose much of the Windows API to Python.
The basic Python distribution includes a manual called Extending and Embedding the Python Interpreter, which describes the process in detail. Chapter 22, shows you how to work with Python at this level on Windows.