An example of a script-not an expression. For example, this script tells the application (the application being After Effects) to position the anchor point of this layer to the center, the right, or the top. Now, unlike a script, which tells the application to do something, an expression will inform the individual property to do something. First, before we look at what the wiggle expression does, we must ask: What is an expression? An expression is a piece of JavaScript code that you can insert into the animated properties of your media.