The Eclipse ADT Bundle provides everything you need to start developing apps, including the Android SDK tools and a version of the Eclipse IDE with built-in ADT (Android Developer Tools) to streamline your Android app development.
ADT integrates many development workflow tasks into Eclipse, making it easy for you to rapidly develop and test your Android applications.
Many of the SDK tools are integrated into Eclipse's menus, perspectives, or as a part of background processes ran by ADT.
The Java programming language editor contains common IDE features such as compile time syntax checking, auto-completion, and integrated documentation for the Android framework APIs. ADT also provides custom XML editors that let you edit Android-specific XML files in a form-based UI. A graphical layout editor lets you design user interfaces with a drag and drop interface.
You can access documentation by hovering over classes, methods, or variables.