A frequent irrgegular verb conjugation is that of the changing root. Some very frequent verbs such as poder (to be able to) and pensar (to think) are conjugated with a root change. Because of this, it is very important to know for which verbs roots have to be changed in order to make a correct conjugation. If you don’t, it might lead to misunderstandings, or not understanding at all. If you’re in a restaurant and would like a glass of water, isn’t it much more fun to ask ‘Puedes traerme un vaso de agua?’ (could you bring me a glass of water?) than saying ‘agua’?