If you start a program in a terminal (usually a graphical one), you can "detach" it from the terminal, allowing you to close the terminal while leaving the application running. To do this, press Ctrl+Z in the terminal after starting the application, then run bg to background it, then disown to detach it. Then you can close the terminal or run exit and the application will keep running.
If you haven't launched the program yet, you can do this in one go with program & disown - the program will start, and you can close the terminal without also closing the program.
