What is the importance of the shadows in Plato's analogy of the cave?

In Plato's famous allegory from his REPUBLIC, the shadows on the cave walls were appearances mistakenly thought to be real by ordinary people. It will help to update his allegory. Suppose that you were born and raised in a movie theatre. All you ever saw of the outside world were movies projected onto the screen. You would naturally, and mistakenly, think that the pictures of, for example, lakes, mountains, and trees you saw on the screen were what lakes, mountains, and trees really were. However, if you were to escape from the movie theatre and go outside, you would only then experience what real lakes, mountains, and trees really were. According to Plato, it's the work of philosophers to escape into the real world and then to help other people escape also. After all, experiencing lakes, mountains, and trees in real life is much better than merely seeing pictures of them