Android Introduction

Android is an operating system for smartphones and tablet computers which is based on Linux, developed by Google.
Google releases the Android code as open source, under the Apache License. The Android Open Source Project, led by Google, is tasked with the maintenance and further development of Android. Additionally, Android has a large community of developers writing applications that extend the functionality of devices, written primarily in a customized version of Java. They are available for download through Google Play or third-party sites. In September 2012, there were more than 675,000 apps available for Android, and the estimated number of applications downloaded from Google Play was 25 billion.

Version of android:-

Version	Release date	API level	System Requirement	Distribution (October 2, 2012)
4.1.x Jelly Bean	July 9, 2012	16	1 GB RAM Dual Core Processor above	1.8%
4.0.x Ice Cream Sandwich	October 19, 2011	14-15	512 MB RAM  1 GHz Processer or above	23.7%
3.x.x Honeycomb	February 22, 2011	11-13	256 MB RAM 600 MHz Processer or above	1.9%
2.3.x Gingerbread	December 6, 2010	9-10	256 MB RAM 600 MHz Processer or above	55.8%
2.2 Froyo	May 20, 2010	8	256 MB RAM 600 MHz Processer or above	12.9%
2.0, 2.1 Eclair	October 26, 2009	7	256 MB RAM 600 MHz Processer or above	3.4%
1.6 Donut	September 15, 2009	4	190 MB RAM 600 MHz Processer or above	0.4%
1.5 Cupcake	April 30, 2009	3	190 MB RAM 600 MHz Processer or above	0.1%

Major brands who makes Android to rule over the top of the world of smartphones are:- 

HTC                          (the first brand that use Android as an OS.)
Google Nexus          (the first brand that real compete with Apple's iPhone.)
Samsung                   (the first brand that help to make possible to reach to the general people at low price with good brand and service & make it common like GPS technology to general hand at worldwide level.) 

These are the brands that shows the people about what is android. And it reach every corner of the world. And these are the mile stones of android world.