Ordinarily, the scope rules for a module govern what can be seen outside of the System, Program, Driver or a Form.
The exception to these scope rules is when a submodule, procedure, variable, or event is marked as being Public. In this case, the submodule, procedure, variable or event is visible throughout ATEasy's namespace.
For example, a System can use any Public Driver; Drivers can use Public Systems and Drivers. You can use any submodule marked as Public from anywhere else. By contrast, non-public symbols can only be used within the same module.