The key words of the paper are the key words of your article content. Keywords are selected from the title, abstract and text of the paper, which are words with substantial meaning to express the central content of the paper. Keywords are words used by computer systems to index the content characteristics of papers, which are convenient for information systems to collect and provide readers with retrieval. Generally, 3-8 words are selected as keywords for each paper, and a new line is set at the bottom left of the "abstract". The key words of the paper should be concise and summarized, and words with no practical significance such as function words and adjectives should be avoided. Subject words are standard words. When determining the subject words, we should analyze the theme of the paper and convert it into standard words in the thesaurus according to the rules of indexing and collocation.