Abstract is a simple protocol. The author summarized the main contributions of his article in the abstract. After reading the abstract, readers can probably determine whether it is necessary for them to continue reading (for example, they can skip articles that are not in their own field).

Keywords are mainly for retrieval services. If you know something about information retrieval, you will know that the principle of search engine is basically based on Boolean retrieval. Boolean retrieval needs to maintain an inverted retrieval table, and for each word, record all the document serial numbers containing it. Then the result document set is obtained by parsing search words and Boolean operations (of course, sorting is also needed).