This document discusses extending the PowerShell shell through modules, snap-ins, and cmdlets. It explains that PowerShell can be extended to handle all types of administration tasks, similar to how the Microsoft Management Console (MMC) provides a single interface. The document outlines how to find, add, and discover new modules and snap-ins to incorporate their commands into PowerShell. It also provides an overview of how cmdlets work in the real world to extend the shell's functionality.