This document provides an outline and overview of the Android operating system. It begins with an introduction to mobile operating systems and lists some examples. It then discusses the origins of Android in 2003 and the Open Handset Alliance formed by Google and other companies to support an open source platform. The document outlines Android's architecture including its use of Linux, Java, and other components. It provides details on Android versions and their features over time. It also discusses developing apps for Android and compares Android to other mobile operating systems.