Window Manager
Kadu
Window manager is a program that allows changing the position, size of windows and also opening, closing and many other window related functions.
Window manager is responsible for window decorations allowing you to manipulate window's behaviour (minimalizing, maximalizing etc.).
Fluxbox, Enlightenment, Awesome, DWM are just a few of many available window managers.
KDE and Gnome are not just window managers. These are desktop environments which include window managers (Kwin is a default window manager for KDE and Sawfish is for Gnome).
