Help to Communicate between a Server and an Android App

Question

I’m developing an android app based on:

• Add/Send DATE to Server
• Collect/Receive Server DATE
• Send and transmit location information( Geolocation )
• Sharing of Profiles

I was suggested to Use JSON (Based Object) and pass it on to android app. But I have no idea how :

• How an Android App running on your Phone asks for JSON "Objects" ?
• How to send DATA from android to server ? How this process works.
• If there is some kind of specific Program, or and to the taste of each ?
• If a "Homemade" Server serves ?
• If the Server has to be prepared to receive DATA JSON ?
• If it is very complicated to transmit Android->Server / Server->android, location information (Geolocation), what are the main procedures ?

I really enjoyed with a help on these topics, or some link of some Web page that I could help myself.

I would appreciate a good answer :) Thank you very much in advance !