Saving Data on Android

Firebase Real/me Database
By Dean Djermanović
Having a central place for storing application data is a common requirement for 
mobile applications. Let's say you're building a mobile game and you need to save 
user progress. You can save it locally on the phone. But what if the user logs in with 
the same account on a different device? That device doesn't know that the user has 
already made some progress and the user will need to start the game all over again. 
That can lead to unhappy users and bad app reviews.
In this case, you would need to save user progress to a remote database so that users 
can have access to the data from any number of devices they own. That database is 
usually hosted somewhere, on the Internet, making it accessible through a simple 
network connection. This concept is known as the 
cloud
. You can think of the cloud 
as someone else's computer, or an entire infrastructure, which you've rented for 
various services.