Android is a  mobile operating system Based on the Linux kernel developed by Google and later the Open Handset Alliance  (OHA).Allows writing managed code in the Java language. 

Unveiling of the Android platform was announced on 5 November 2007 with the founding of OHA. firstly Android was developed by the Andy Rubin, Rich Miner, Nick Sears and Chris White  in Palo Alto, California on  October, 2003.

and then Android was purchased by the GOOGLE in AUGUST,2005 for 50 million $.

"Open Handset Alliance™, a group of 84 technology and mobile companies who have come together to accelerate innovation in mobile and offer consumers a richer, less expensive, and better mobile experience.“               

                                                               Quoting from www.OpenHandsetAlliance.com page

Bassically It's a consortium of several companies who worked on innovations of android mobile operating system.they have  developed Together and committed to commercially deploy handsets and services using the Android Platform.It was established on 5th November, 2007, led by Google.