You will learn more about this later, but there are a lot more elements at play when creating a complex program. Think about it like when you create a game every action is defined. Those are methods, they are used everywhere and we use lots of tools to reduce redundency when using varing actions.
Methods are the meat to any program.
The key to "Complex Programs" is that it really is just as simple as what you are doing with methods now, but in a complex program you can expect thousands of lines or codes that you need to maintain. Soon you will learn later how to better organize your code and breakup parts so that your programs function, are robust, and reduce redundency.