Screen is a 'terminal multiplexer', it allows you to turn one terminal into many all self contained. Nohup will continue command execution until completion (or failure, either way a program exit), and then it'll go away.
Or you can learn how to use the 'screen' command. One is that you can use the 'nohup' command to continue command execution even if the shell goes away. You have two options, and both may be a bit more involved than you want to be. (Applications don't run without a controller of some manner.) Using & puts it in the background of the shell, but if you kill the shell, you kill that application as well. Don't worry that you're doing something wrong.
