screen is a little command that I use on a daily basis, it allows you to start a session, execute some commands, disconnect from the session while the command continues and later reconnect to it.
Starting a screen session
To start a screen session you just hit screen. Then you start whatever you need to run. By hitting ctrl+a and followed by d, you detach from your session. You see the session ID when you have exited the screen session, you will need this ID to reconnect to it.
Listing your sessions
If you have multiple sessions and want to have an overview you run screen -ls.
Reattaching to a session
When you come back and want to reattach to a session you do screen -r .
Killing a session from within a session
When you are in a session you can kill it by hitting ctrl+a and then k.
Killing a session from outside a session
When you want to kill a session from outside a screen session you do screen -X -S