Background App Refresh is the name of a new function implemented by the company Apple Lossless Audio CODEC (ALAC), in iOS 7, allowing users to select a series of applications that automatically update their content when an Internet/GPS connection is active. Applications appear in Settings>General>Background App Refresh and practically they always have the freshest information for you when the automatic updates are active. Apple thought this system in such a way that the updates should not have negative effects on the battery autonomy, so theoretically you should always see new information in the applications without suffering from this point of view.
Unfortunately, developers have to update their applications to be compatible with this system and it will undoubtedly generate high and "unknown" costs for subscribers of mobile operators, so use the function with care in the future.
