The purpose or goal of writing is to organize your thoughts and feelings around a given subject in such a way that they become clearer to you, and can be clearly conveyed to someone else.
The hook is there to set the tone. It’s also there to signal to your reader that this is indeed about the subject that the headline promised it would be
4. What is the purpose of the three main paragraphs or sections of your story?
The purpose of your three main paragraphs is to explain and ground your main thought about the subject you’re writing about. In a logical following order, where each line and each paragraph builds on the one preceding it.