The iPhone revolutionized the world of mobile application development. However the iPhone’s proprietary hardware and software development environments are a roadblock to many. Google’s Android platform with its promise of open standards for hardware and a free and familiar development environment make it a strong contender for competing with the iPhone platform. After introducing the Android platform we will discuss the paradigms and constraints in building a mobile application. We then dissect a simple “social” Android application which uses a REST-based webservice to communicate. This will help us understand the core components of an Android application and the Android SDK functionality.