it is by many considered good practice to write academic papers with a threefold structure, consisting of an introduction, a main part, and a conclusion. in addition, you are often expected to include an abstract with a summary of the content at the beginning of the paper.
i think that this structure is in fact often a bad idea, because it leads to a lot of redundancy. the result is a paper like this:
Abstract: In this paper it will be shown that chicken lay eggs.
Introduction: We are going to show that chicken lay eggs.
Main part: Chicken lay eggs.
Conclusion: We have shown that chicken lay eggs.
come on, i’m not stupid, there’s no need to tell me the same thing four (!) times. if you don’t have anything to say in the introduction or the conclusion, then skip it, but don’t just repeat what you have said elsewhere pro forma, sometimes even reusing the exact same wording multiple times! i don’t want to read that, and the author(s) probably don’t want to write it, so why not just concentrate on the relevant parts? looking at the “paper” above, isn’t in fact everything relevant included in the main part?