How server communication is handle?

I am very confused state. In my app there will be some database on server, from this database data will be fetch and w开发者_如何学JAVAill display in my app. Please guide me, what data base should be used on server then how the communication will establish then how data will fetch then display in app.

I am totally in blank. Plz help me out.

---

You must create a web-service, and try connecting iPhone to web service.