First Android Application, Hello World

This is my First android application so i explain shortly and easy to  understand for android learners.We can be very convenient to use ADT to create an Android Helloworld application.

An Introduction to Android

Introduction
Android is an open source mobile operating system that combines and builds upon parts of many different open source projects. what does it mean to you as developer? you have access to the source code of the platform that is running on the phone. This can help you better understand how interface controls and the various other pieces work. If you happen to find a bug you can also submit a patch for the issue though this is a more advanced practice.Google has also pulled together a large group of companies(called the open Handset Alliance) that both contribute to and use the Android OS in their hardware devices. This means that there is industry-wide support for Google's OS, promising wide adoption across well-known vendors .

Android has a large community of developers writing application ("apps") that extend the functionality of the devices. developers write primarily in a customized version of java.