Android is an operating system for mobile devices whose project started in 2005, supported by Google colossus and an alliance of several companies (Open Handset Alliance) interested in the opportunities offered by an open system in the market. Indeed, Android is a project that follows the Open Source development model (in particular under the Apache License 2.0 plus a little something in the GPL), and which also is based on the Linux kernel.
Android was presented to the public in 2007, together with the birth of OHA. The first release came about a year later, with version 1.0, and since then the trend was unstoppable, with new versions released every few months and with a market in this expansion that creates uphill battle between his supporters and those of his direct competitor, the iPhone.
Owners of an Android device have access to the Android Market, a service that allows software developers to easily sell their own applications for Android phones, and users to pick from the vast choice of games and apps.