Up until now we approached objects and functions directly and that was very useful until now. For us to be a able take the next step as developers, we need to create code that is more reusable.

A good example to this would be, a great teacher that sits and teaches a student and gets paid 50 bucks. Another teacher, that is just as good, creates a video course and then sells it to masses for 10 bucks. While both may be great teachers, one of them is more efficient and thus more profitable as he helps more people. This is exactly the same thing as what we're going through right now. Up until now, most of our developments were a one time hit, but for us to become great developers and leverage this new skill, we need to learn how to reuse our code.