Urgent things may not be important but must be taken care of “urgently” such as the kettle boiling! But important things, though must be made more certain to be done on time, may not be urgent enough for one to drop everything, especially “urgent things” to do. “By-the-way” things are really not urgent and not important so that you will do this only if you have made certain that the important things and/or urgent things that you are supposed to do are “made more certain” of happening!