Book excerpt: ‘Learn Android’ covers basic and advanced concepts of android technology. It is developed for beginners and professionals. Android is a complete set of software for mobile devices such as tablet computers, notebooks, smartphones, electronic book readers, set-top boxes etc. It contains a linux-based Operating System, middleware and key mobile applications. It can be thought of as a mobile operating system. But it is not limited to mobile only. It is currently used in various devices such as mobiles, tablets, televisions etc.