OutSystems Sample Data is a module that contains entities and sample data to accelerate application prototyping and development.
It's used on the new Screen Templates, so when a new screen is instantiated, it can be published and working in a matter of seconds. But it can also be used in any other applications and screens.
Similar to the OutSystems UI modules, it is a system module and cannot be changed, however, it's possible to export the original data, change it and import it back.