Android Development Tool (ADT) is a plugin for the Eclipse IDE that is designed to give a powerful, integrated environment in which to build Android applications.

ADT extends the capabilities of Eclipse to let the developer quickly set up new Android projects, create an application UI, add packages based on the Android framework API, debug the applications using the Android SDK tools, and even export signed (or unsigned) .apk files in order to distribute the application.

Developing in Eclipse with ADT is highly recommended, and is the fastest way to get started. With the guided project setup it provides, as well as tools integration, custom XML editors, and the debug output pane, ADT gives an incredible boost to developing Android applications.

However, ADT support for Eclipse is being pulled by Google, so developers are recommended to switch to Android Studio.