Writing requires a tremendous amount of work and that work often happens in phases. If you were to look at the first drafts of Hamilton or Harry Potter, they would look undeniably different from their final products. First, you brainstorm. Then you create outlines about your story, the characters, the plot, and every other detail imaginable. Writers do this several times in several different ways. Then they write the first of many drafts. Ken Miyamoto with ScreenCraft discusses the difference between outlines, treatments, and scriptments and how each of them is important to the story development process.
Read the full article here: Outlines, Treatments, and Scriptments, Oh My!