Eclipse provides a lot of basic functionality, particularly for Java development. However, Eclipse also provides the ability for any user to extend its functionality through the installation, use, and development of plug-ins. A plug-in is a small piece of functionality that can be added to Eclipse that allows a user to perform a small task. An example plug-in into Eclipse is JUnit.

In order to plug-in to Eclipse, you must create an extension of an already available component in Eclipse. For example you can add an action (a button that displays a dialog or does some task) or by creating a new view, both of which extend an existing perspective in the Eclipse workbench. Another example would be to extend Eclipse by creating a new perspective with new views that performs some functionality.