title: How does facebook or instagram app retain images or data after entering the app with no internet connection?
body: <p>In Facebook app, for example, I login with my internet connection. Then I close the app, turn off the internet and close all my system tabs. Then even though my internet connection is off, I see the images and data that had been previously loaded still retained.</p>
  
  <p>How does Facebook app do that? What should I do if wanted to implement such a feature in my Android app?</p>