XMonad is a tiling window manager for X11. The document discusses the author's journey through different window managers and their setup using XMonad. They find XMonad's defaults suit them well and appreciate its extensibility through Haskell. They use multiple monitors with XMonad, dedicating one to a single focused window and the other to auxiliary windows. To better organize their many terminal windows, they switched to using tmux which allows multiple terminal sessions in one window through multiplexing.