PowerShell has many built-in Cmdlets that provide information about the language itself. When you're learning PowerShell, you'll likely find the following Cmdlets helpful:
Aliases. PowerShell supports aliases that you can use to reference Cmdlets. For example, you can use Foreach or % to reference the Foreach-Object Cmdlet. For a list of aliases, enter
Get-Alias at the PowerShell command prompt. For general information about aliases, enter
Get-Help About_Alias Cmdlets. For a list of Cmdlets, enter
get-help -category Cmdlet To retrieve detailed information about a Cmdlet, including the parameters it supports, enter
get-help CmdletName -detailed where CmdletName is the name of the Cmdlet you want to get information about. For example, to retrieve information about the Get-Service Cmdlet, enter
get-help get-service -detailed ForEach-Object Cmdlet versus ForEach statement. the Foreach-Object Cmdlet and Foreach statement aren't the same. to learn how they differ, enter
Get-Help About_ForEach Help. to retrieve information about how to use PowerShell help, enter
Get-help get-help Operators. to learn about operators (e.g., -replace, -gt, -ne), enter
Get-Help About_Operator PowerShell security. to learn about PowerShell security, enter
Get-Help Set-ExecutionPolicy WMI classes. For information about how to access WMI classes, enter
Get-Help Get-WMIObject 
