One of the hallmarks of Joyce's style is the way that he uses epiphanies in his endings to this collection of stories. All of them end with an epiphany, which can be defined as a moment of sudden insight or revelation experienced by a character. Interestingly, before Joyce coined the phrase to refer to his literature, an epiphany only referred to a religious experience, a moment during which a person felt intense connection with the divine or understood an important truth that he hadn't before.
Thus it is that the protagonist in "Araby," for example, experiences a sudden moment of insight at the end of the tale, realising his own insignificance of his hopes and dreams:
Gazing up into the darkness I saw myself as a creature driven and derided by vanity; and my eyes burned with anguish and anger.
Likewise, Gabriel in "The Dead" has a similar experience at the end of the tale as he processes what Gretta, his wife, has told him about Michael Furey and he realises his own shallowness and superficiality.