The KDE Plasma Desktop
This is the basic KDE Plasma desktop. These applications are common programs usually found in base KDE SC 4 installations. They provide core desktop environment functionality. These KDE base programs allow users to operate, manage and control their desktop and programs easily and flexibly.
The Pillars of a KDE Platform
There are other parts of the KDE platform that work "under the hood" to give you the best desktop experience. You might be interested in knowing about them.