Hey,
Sometimes the app will throw one based on syntax errors. Exceptions are raised when an error occurs within your data. For example, if a user enters bad data, you can throw an exception. You can make your own exceptions by creating a class that inherits from System.Exception.
Just like Err.Raise in
VB, except you do THrow New <exception> to do it in .NET. Exceptions that aren't handled with try catch block are then visible in the browser/form.
Hope this helps,
Brian