KWin (pronounced as one syllable "kwin") is the window
 manager for the KDE Plasma Desktop. It gives you complete
 control over your windows, making sure they're not in the way
 but aid you in your task. It paints the window decoration,
 the bar on top of every window with (configurable) buttons
 like close, maximize and minimize. It also handles placing
 of windows and switching between them.
 .
 This package is part of the KDE base workspace module.