Android is a software stack for mobile devices that includes an operating system, middleware, and key applications. The Android SDK provides the tools and libraries necessary to begin developing applications that run on Android-powered devices. This site provides information about Google projects based on the Android platform, such as external libraries that extend the platform, hosted services and APIs, and more. Everything on this site is provided by Google for the benefit of Android developers. If you are interested in developing applications for Android devices, please visit the Android Developers site at developer.android.com which contains the following information. The Dev Guide provides a practical introduction to developing applications for Android and documentation about major platform features. It explores the concepts behind Android, the framework for constructing an application, and the tools for developing, testing, and publishing software for the platform. The Dev Guide is divided into several sections: Android Basics An initial orientation to Android — what it is, what it offers, and how your application fits in. Framework Topics Discussions of particular parts of the Android framework and API. For an introduction to the framework, begin with Application Fundamentals. Then explore other topics — from designing a user interface and setting up resources to storing data and using permissions — as needed. Android Market Topics Documentation for topics that concern publishing and monetizing applications on Android Market, such as how to enforce licensing policies and implement in-app billing. Developing Directions for using Android's development and debugging tools, and for testing the results. Publishing Instructions on how to prepare your application for deployment and how to publish it when it's ready. Best Practices Recommendations on preferred techniques for writing applications that perform efficiently and work well for the user. Web Applications Documentation about how to create web applications that work seamlessly on Android-powered devices and create Android applications that embed web-based content. Appendix Reference information and specifications, as well as FAQs, a glossary of terms, and other information.