A log line will serve different, though equally important, purposes depending on what role you are playing in the creative process. For a producer, a log line is the crucial first line of defense when it comes to selling a project. It’s what initially grasps the attention of the buyer. Many times, especially if you are not an established producer/director, a studio will want the log line and synopsis of your project before they will take a pitch from you. You must be able to convey what your story is about in one concise sentence. If you are unable to do this, your project is probably not very good, or you need to further develop your story.
If you are a writer, a log line is crucial for keeping you focused on your story during the writing process. Many times, writers will become too engrossed in dialogue or character, that they will lose sight on what the story is.