Professional Windows® PowerShell

6.4. Summary

When you use a Windows PowerShell cmdlet, you will often use the cmdlet with one or more parameters. A Windows PowerShell cmdlet's parameter is supplied as a name immediately preceded by a hyphen. The value is separated from the name by one or more whitespace characters. A parameter's value may contain multiple elements separated by commas.

Named parameters are parameters whose name must be supplied. A positional parameter (of which a cmdlet may have none or more than one) can be interpreted by the PowerShell parser without the parameter's name being specified.