You may control when module is loaded. As a default, the users module is loaded 1st as it is needed by all other modules. The layout module is loaded last (priority 99) because it finalizes the page. If it doesn't matter when you module is loaded, just enter 50. If your module is dependant on another module loading, enter a priority higher than that module. Enter a lower priority if another module depends upon yours. Remember that all classes are loaded when the program is started, so you may be able to access functions in a class without the module loaded.