Have you ever been working on a server or Linux computer over an SSH connection and then lost the connection? Backups lost, apt-get dist-upgrade in an unknown state, and unable to reconnect: this is a nightmare of many system administrators.
Along comes the wonderful Linux terminal command: screen
screen allows you to create resumable terminal sessions in the Linux terminal. With screen, you can start a large task and then disconnect, then reconnect later to check on the status or provide user input. The danger of a lost connection are gone since every screen session can be resumed.
You can even use screen to provide your bash session with an enhance multitasking environment: create a screen session and start a task, then detach the session and create another screen session to conduct another task. Then, switch between them.