The beats of a story are the big, important points and the critical moments. Like nails driven into posts, beats are what you tie the clotheslines of a story to so that you can get from the beginning to the middle and the middle to the end. Fill out as many beats as you can. If you have to leave one blank because you don’t know, don’t “beat” yourself up. Oh, and always use pencil when filling out the beat sheet. It’s going to change as time goes on.
Here’s a translation of the beats as they appear in many books: