Every operating systems do have command-line shells, and those are specially designed for system administration. Most shells which accepts commands and returns text. But shell of Windows is very powerfull and that is why it is called PowerShell, it accepts objects and it returns objects. Becuase Windows PowerShell is built on top of the .NET Common Language Runtime (CLR) and because of this it introduces new tools and methods for automation.
Windows PowerShell introduces CmdLets, by which it is easy to manage computers from the command line. Even it is easy to manage remote computers from the command line, which could be harder to manage it using GUI.
Windows PowerShell has a scripting language ability too and using that it would be more easy to automate the system administration.