The key point is to introduce the background knowledge, describe the research object, describe the previous research results and existing problems, and finally draw out the author's improvement/innovation points. The introduction aims to describe the research problems, explain the significance and value of the research, and make readers have a macro understanding of the problems and solutions.
Make a metaphor that may not be appropriate:
If the abstract is compared with the trailer before the film is released, people can get a general understanding of the story of the film.
Introduction is like the opening part of a movie, characters begin to appear and the audience is gradually brought into the scene of the movie story.