The document discusses the use of reference words in writing, which help avoid repetition by referring back or forward to previously or subsequently mentioned people, objects, and ideas. It covers specific reference words such as 'it', 'they', 'this', 'that', 'the former', 'the latter', 'who', 'which', and 'one', along with examples of their usage. Additionally, the document highlights how these references clarify meaning and improve coherence in written communication.