Eclipse is a platform which is itself comprised of plugins.Eclipse itself is not only a Developement environment for Java pr C++ But also an IDE for plugins for itself or standalone plugins.
As stated above Eclipse can be used as a Plugin Development Environment (PDE) which is a set of tools that help the developers in developing, testing, debugging, building, and deploying Eclipse plugins.
The plugin Development Environment (PDE) has its Wizard template to create plugins. The plugin,to be created will associate Eclipse with the file extension “.myext”. The plugin’s wizard will enable the user to create files with this extension, and when the user double-clicks on those files, they’ll appear in the plugin’s editor.