Screen is one of those unique tools which you don't know you'll need it until you use it. Screen does for terminal sessions what VNC/PCAnywhere/RDC/RAdmin does for the GUI. Difference is screen was around first. Multiple connections into a single TTY, detaching from the TTY and attaching from another location, multiple virtual TTYs from a single physical TTY, multiple TTYs on a split screen, all possible with Screen. This simply is a tool every terminal jockey must be familiar with even if they do not use it on a daily basis.