Any application that provides users with some form of data that updates over time is able to implement background fetch. An application that implements background fetch is woken up by iOS periodically, and it's given a small window of time to fetch and process new data that has become available. The OS expects applications to call a callback when they're done with fetching and processing the data. The application uses this callback to inform the OS about whether or not new data was fetched. We'll take a look at a broad overview of background fetch first and then we'll highlight each of the moving parts in more detail before implementing background fetch in the FamilyMovies application.