The moon has two sides, one – as Pink Floyd sang – which we never see, but we know the other side well. Software often also has two sides. The backend is its dark side, hidden and accessible to few, while the frontend is the side we interact with every day.

Every device that has a screen usually has a frontend, sometimes called User Interface (UI). These two concepts are very similar and are practically synonyms. Frontend is a term that the experts usually use. For the developers it is the code that manages the functions related to the interface and its aspect, while for the designer it is more generically what the user sees on the screen.

The frontend is designed to adapt to the device that must display it and this implies that each device must have a specific interface or that it adapts dynamically based on the size of the screen. The frontend has great impact on the User Experience, so it must be designed carefully keeping in mind the needs and the skills of those who use the software.