How to link a website to a mobile app [on hold]

I'm currently learning android app development, and I'll like to build an app when I'm done. OK,here's my question now 1) what other language aside HTML and CSS do I need to learn in other to link my app with a website to receive data...Like posting files and information on a website to display on the app,just like Facebook web and mobile app,but here the app isn't a version of the web....it is basically controlled by the website 2) can I possibly control and maintain the app within the app itself?