Explanation

Box 1: PreValidation
PreValidation: For the initial operation, this stage will occur before the main system operation.
This provides an opportunity to include logic to cancel the operation before the database transaction.
Box 2: Synchronous
Ideally, you should only cancel operations using synchronous plug-ins registered in the PreValidation stage.
Box 3: Pre Image
Box 4: throw ..
When you throw an InvalidPluginExecutionException exception within a synchronous plug-in an error dialog with your message will be displayed to the user.
Reference:
https://docs.microsoft.com/en-us/powerapps/developer/common-data-service/event-framework
https://docs.microsoft.com/en-us/powerapps/developer/common-data-service/handle-exceptions