A window manager is a piece of system software for X that controls the placement of windows within a Graphical User Interface (GUI). They control serveral features of the GUI, such as the borders, title bar, size and the ability to resize the windows. They can be provided as a part of the desktop environment, such as Kwin in KDE Plasma, with features such as icons and toolbars and the ability to provide a more consistent User Interface (UI). Or they can be standalone (such as i3) to give the user the ability to create a more lightweight and customised environment at the cost of requiring the user to add the desired software. There are 3 main types of window managers: #Stacking/Floating provide the traditional desktop experience such as Xfwm in XFCE, #Tiling where the apps 'tile' so none overlap often with minimal or no reliance on the mouse such as AwesomeWM and #Dynamic which can switch between stacking and tiling window layouts such as Dwm.