In Windows PowerShell 2.0 (the November 2007 Community Technology Preview release) the PowerShell team has taken an interesting approach to script debugging. As you know, PowerShell doesn’t require a specialized script editor or development environment. Instead, PowerShell users can, and do, use any and all text editors (from Notepad on up) to write their scripts. Because of that, the PowerShell team decided to build their debugging tools into Windows PowerShell itself; in turn, that means that you can use the new debugging cmdlets to debug any script from the console window itself.

Complete Reference: http://technet.microsoft.com/en-us/library/ff730925.aspx