Okay kiddo, have you ever heard someone say that something is the "golden line"? It means that it's the best way to do something. Think of it like a treasure map, but instead of leading you to treasure, it's showing you the best way to get something done.
Sometimes people need to find the golden line so they can be more successful in what they're doing. For example, if your teacher tells you to write a book report, the golden line might be to read the book first, take notes, and then organize your thoughts before you start writing. Following the golden line will help you write the best book report possible.
So, when you hear someone talking about the golden line, just remember that it's a special way to do something that's better than any other way. And if you follow it, you'll be sure to do a great job!