Writing source code is like applying bricks in construction, it is the production material necessary to achieve something. As with construction there are blueprints necessary to build a serious construction, we call these APIs (application programming interface) in computing. I have built up decent experience with designing a technical architecture before just writing code to ensure that the end result doesn't just run now, but that it persists over time
A proper designed software application separates data, logic and presentation. This principle - model view controller (MVC) - ensures that a built piece of software consists of independently testable pieces. These layers are able to interact with each other but due their separation, are also easily replaced.