The phrase "useful applications" refers to programs or software that are designed for specific purposes and provide benefits, solutions or value in performing tasks. These can range from productivity tools such as word processors, spreadsheets, presentation software, and databases; to entertainment apps like music players, video streaming services, and games; to utility apps such as maps, weather forecasts, and online shopping platforms. Essentially, any app that provides a solution or performs a task efficiently can be considered useful in its application.