As an experienced IT professional, you must be familiar to many coding patterns and probably have used code templates. If you have prior experience with templates, it may help you to think about Code Model as a smart template that compiles and works on its own.
Code Model is the IDEAL code you want to use as the basis of your application. Think of it as blueprint that would build code for you. Typically that would be an application that works with Base Data Model.
Code Model can consist of anything from Single File to a Complex Project having multiple folders and files (including Tests) possibly across different application layers and may involve multiple programming languages.