Form-level constants are designed to be used by a specific form in the application. You should use a form-level constant when several scripts on a form use a constant, but there is little need to use the constant elsewhere in the application.
Within the scope of a form, you can reference a form-level constant directly. To reference a form-level constant from outside the scope of a form, use the qualifier of form form_name. If a form-level constant and a global constant have the same name, by default, scripts attached to the form will use the form-level constant. To refer to the global constant instead, use the qualifier of globals following the name of the constant.