The Gist shows two examples of custom PowerShell errors.

CustomPSErrors.ps1

# Example 1 - Catch the exception that would have been thrown after a method such as connecting to a SQL database / failed network connection
$errorRecord = New-Object System.Management.Automation.ErrorRecord(
    $_.Exception,
    'SmallOneWordDescriptionOfError', (e.g.ConnectionFailureToDBName)
    [System.Management.Automation.ErrorCategory]::ConnectionError,
    $myinvocation
)
$pscmlet.ThrowTerminatingError($errrorRecord)


# Example 2 - Creating and throwing a custom error for parameters that are incorrect for example
$errorRecord = New-Object System.Management.Automation.ErrorRecord(
    (New-Object System.ArgumentException "The parameter provided is wrong because"),
    'SmallOneWordDescriptionOfError', (e.g.ConnectionFailureToDBName)
    [System.Management.Automation.ErrorCategory]::InvalidArgument,
    $VariableName
)
$pscmlet.ThrowTerminatingError($errrorRecord)