Powershell Write-Output vs return

pipline.test.ps1

clear
function Invoke-First {
    Write-Output 'if not piped, will display before Write-Host, if piped, will display after Write-Host'
    Write-Host 'Writes every single time invoke-first is called, but is not piped out.'
    return 'will not display unless piped or used as a return variable'
}

function Invoke-Second {
    param(
        [Parameter(ValueFromPipeline=$True)] [string] $val
    )
    Write-Host $val
}

Invoke-First
Write-Host

Invoke-First | Invoke-Second
Write-Host

$myVar = Invoke-First
$myVar