What is Android??

--> Is it an Operating System alone??
ans) No. If it is an O.S, it has to support 2 or more Programming Languages. But Android supports only Java.

--> Is it a Programming Language??
ans) No. It inturn relies on Java as a programming Language.

--> Then What exactly is Android??
ans) Android is a Single piece(Applications + Framework + Libraries + DVM + LINUX Lernel) all combined together. All the above things constitute a software stack.

--> Why Android??
ans) To Develop Applications for Mobile Devices.

--> Is Android Platform Independent??
ans) Android itself is a platform :-)
       So there is no meaning in discussing about platform independence.

--> Android is for 
1) Mobile Application Developers - who want to develop innovative applications
2) Mobile Companies - who can get Android at almost no cost(Android is open source & free) and encorporate it in there Devices.
3) Mobile Users - who can easily get their requirements to be solved by consulting Mobile Application Developers & also can get the built in apps to be replaced by the other apps.

--> Finally, Android is a gift given by OHA(Open Handset Alliance) led by Google for the above 3 categories of people.

--> This is the introduction of Android. Hope you got atleast some idea about What is Android and Why Android. Good Day :-)