A child who is a native speaker usually knows many things about his or her language that a non-native speaker who has been studying for years still does not know and perhaps will never know.
Un niño que es hablante nativo normalmente sabe muchas cosas acerca de su lengua que un hablante no nativo que lo haya estado estudiando durante muchos años no sabe todavía y que quizá no sabrá nunca.