Window manager — what it is
A window manager (WM) controls placement, appearance, and behavior of application windows within a graphical environment. It handles window decorations, focus, workspaces, tiling/floating behavior, and keyboard/mouse interactions. Window managers can be standalone (you start X/Wayland with them) or run inside a desktop environment.
Types
- Tiling WMs: automatically arrange windows in non-overlapping tiles (e.g., i3, bspwm, awesome, dwm).
- Stacking/Floating WMs: windows overlap like traditional desktops (e.g., Openbox, Fluxbox, Metacity).
- Compositing WMs / Compositors: provide effects, transparency, and smooth rendering (e.g., Mutter, KWin, picom as compositor for others).
- Desktop Environments (DEs): include a WM plus many integrated components (GNOME uses Mutter, KDE uses KWin).