PowerShell difference between Write-Host and Write-Output?

Write-Output sends the output to the pipeline. From there it can be piped to another cmdlet or assigned to a variable. Write-Host sends it directly to the console.

$a = 'Testing Write-OutPut'  | Write-Output
$b = 'Testing Write-Host' | Write-Host

Get-Variable a,b

Outputs:

Testing Write-Host

Name                           Value                                                                 
----                           -----                                                                 
a                              Testing Write-OutPut                                                  
b                                                  

If you don't tell Powershell what to do with the output to the pipeline by assigning it to a variable or piping it to anoher command, then it gets sent to out-default, which is normally the console so the end result appears the same.

In a nutshell, Write-Host writes to the console itself. Think of it as a MsgBox in VBScript. Write-Output, on the other hand, writes to the pipeline, so the next command can accept it as its input. You are not required to use Write-Output in order to write objects, as Write-Output is implicitly called for you.

PS> Get-Service

would be the same as:

PS> Get-Service | Write-Output