Frontend is the code handling the gui and backend data storage and minipulation. This was done to simplify the code. The backend gets created as an object that will also work as data store. Currently the backend only holds data in RAM but we are going to make backend auto backup to file when changes happen and then reload from file on creation.
This is quite obvious, its much easier for the user to input and read data through the gui. But the gui is far from done it will be improved before the project finishes so that it looks nice and is not only functional design.