The Android SDK provides you the API libraries and developer tools necessary to build, test, and debug apps for Android.
If you're a new Android developer, we recommend you download the ADT Bundle to quickly start developing apps. It includes the essential Android SDK components and a version of the Eclipse IDE with built-in ADT (Android Developer Tools) to streamline your Android app development.
With a single download, the ADT Bundle includes everything you need to begin developing apps:
Eclipse + ADT plugin
Android SDK Tools
The latest Android platform
The latest Android system image for the emulator