Today was the first day I stopped using screen and started using tmux, which is a superior alternative which supports a more complex range of splits and has a nicer interface. It's a bit different from screen in that it has this concept of windows and panes. A tmux pane is a window (e.g., shell session) in screen terminology. A tmux window is a layout of panes (e.g., two windows side by side). A tmux window could have only one pane, or it could have an arbitrarily complex configuration of panes.