From http://www.android.com: Android is a software stack for mobile devices that includes an operating system, middleware and key applications. The Android SDK provides the tools and APIs necessary to begin developing applications that run on Android-powered devices.

The Android site provides information about Google projects based on the Android platform, such as external libraries that extend the Android platform, Android applications, hosted services and APIs, the Android Developer Contest, and more. Everything on this site is provided by Google for the benefit of Android developers.

If you are looking for general information about Android, visit the www.android.com site. If you are interested in developing applications for Android devices, visit the Android Developers site at developer.android.com