The sentence "A book can highlight the past and present, and the moon is divided into three or five shadows" means that the knowledge in the book can make people clearly understand all kinds of things in ancient and modern times, just as the bright moonlight can clearly reflect the shadow of objects. The whole sentence expresses the awe of knowledge and the praise of words. Emphasizing the knowledge in books can make people know more about the world, and writing is one of the important ways to inherit and express knowledge.