KDesktop
Encyclopedia
KDesktop is the component of the K Desktop Environment
that provides a virtual background window
to draw icons or other graphics on prior to KDE SC 4.
It was replaced by Plasma in KDE SC 4.
KDE
KDE is an international free software community producing an integrated set of cross-platform applications designed to run on Linux, FreeBSD, Microsoft Windows, Solaris and Mac OS X systems...
that provides a virtual background window
Root window
In the X Window System, every window is contained within another window, called its parent. This makes the windows form a hierarchy. The root window is the root of this hierarchy...
to draw icons or other graphics on prior to KDE SC 4.
It was replaced by Plasma in KDE SC 4.