A window is an opening in a building or vehicle. Many windows have glass to keep inside and outside separated. Those inside can look out through a window. Those outside can look in through a window. Usually the window glass can be opened to allow the inside and outside to mix. Building windows often have screens so that when the glass is opened bugs remain outside. Vehicle windows are opened and closed with electric motors. Older windows may have a manual crank for opening and closing.
A manager controls a portion of a business. Managers who think of themselves as important may not be liked by those being managed.
A manager who works for a company that makes windows is a window manager.
Linux is an operating system, which manages the resources of a computer. The display of a computer is a resource. Users interact with Linux via windows on the display. A window manager controls windows on a Linux display. The window manager allows users to create, move, resize, and delete windows. Linux has many window managers to select from. KDE, Cinnamon, Gnome are three.
Do you like windows? Do you like managers? Do you have a favorite Linux Window Manager?