PowerShell is a scripting language written on the .Net framework by Microsoft. Some would say, the new and improved Microsoft Command shell.
A version of PowerShell has been available for Microsoft Operating Systems since Windows XP. It can be used for system/applications automation and administration.
It has direct access to COM and WMI. So basically the possibilities are up to your imagination.
Use it for simple administration, incorporating your own functions, or creating tools for others.
Microsoft's Technet library article Scripting with Windows PowerShell.
There are a lot of scripts ready to use or manipulate to your own needs located in the Windows PowerShell Script Repository.