Allusion is a literary device commonly used in literature to refer to people, places, and events in other works of art. It can be used as an indirect reference or comparison to add depth and richness to the work. Allusions are often subtle and not always immediately recognizable by readers; they may require some familiarity with the source material being alluded to for them to be understood fully. By using allusions, authors create a bridge between their work and others that have come before it, allowing them to further explore themes or ideas without having to explain them directly.
In addition, allusions can also provide insight into the author's own personal opinions on topics such as religion, morality, history, etc., as well as give an indication of how knowledgeable they are about certain subjects due to the references they make within their writing. For example, when someone makes a biblical allusion in one of their stories, it could suggest that they believe strongly in Christianity or at least have studied its teachings closely enough so that they can make comparisons between characters from different books, stories, plays, etc.
Allusions are usually quite short but powerful statements that add another layer of meaning behind what is written on the page, ultimately making any piece of literature much richer than if only direct words were used throughout the text. This literary technique has been employed by writers since ancient times and continues today, proving just how effective this form of communication really is.