In computer programming, Eclipse is a multi-language Integrated development environment (IDE) comprising a base workspace and an extensible plug-in system for customizing the environment. It is written mostly in Java.
The Eclipse SDK includes the Eclipse Java development tools (JDT), offering an IDE with a built-in incremental Java compiler and a full model of the Java source files. This allows for advanced refactoring techniques and code analysis. The IDE also makes use of a workspace, in this case a set of metadata over a flat filespace allowing external file modifications as long as the corresponding workspace “resource” is refreshed afterwards.
It is already included on the SDK-ADT bundel for windows that you can download it from android developers website.
Download | SDK
But if you want to download it separately you can also download it from Eclipse website.
Download | Eclipse