The preface, also known as "preface", "preface" and "introduction", is an article placed before the main body of the work. The preface written by the author himself is called "self-preface", and the content explains its content, reason, process, purpose and characteristics; the preface written by others is called "preface", which mainly introduces and comments on the ideological content and artistic features of the book. The former is like Lu Xun's "Preface to "Scream", and the latter is like Mao Zedong's "Preface to "Rural Survey". The language expression method is relatively flexible. You can focus on one expression method, or you can use multiple expression methods comprehensively. For example, "Preface to Rural Survey" is mainly about discussion, Wen Tianxiang's "Preface to "Guide Record" combines narrative and lyricism, and Sun Yat-sen's "Preface to "The Story of the Seventy-two Martyrs in Huanghuagang" combines narrative, lyricism, The discussion merged into one. In ancient times, there was another kind of preface that was a farewell message, called the "gift preface". The content was mostly words of approval, praise, or encouragement for the relatives and friends to whom the gift was given. It was a style of farewell message. For example, Song Lian's "Preface to Ma Sheng in Dongyang" is the author's preface to the younger generation in his hometown. There is also a preface written in front of the poem, called the "poem preface", which mostly explains the content of the story being chanted or the origin of the poem. For example, the Han Yuefu "Peacock Flies Southeast", Bai Juyi's "Pipa Play", and Jiang Kui's "Yangzhou Slow" all have a preface.