Very few mobile apps are completely independent of external data: think of the apps you use for weather forecasts, listening to music, reading books, news, or emails. They all have something in common: they rely on data taken from an external source. The most common source to get data from a mobile (or any client) app is called a web service or web API.
What happens is that a client app connects to a web service, makes a request to get data, and if the request is legitimate, the web service responds by sending the data to the app, which then will parse the data for its features. The advantage of this approach is that developers only need to create and maintain one source of data and can have as many clients as needed. Actually this pattern (client/server) is nothing new, but it's extremely common when designing apps...