When you close an xterm window, what happens to the process running in it?
Usually it dies, but why?
Because xterm arranges to send a HUP signal to the process
The default behavior for receiving a HUP is to die instantly
HUP is short for 'hangup'
Originally delivered automatically by the kernel when you hung up the modem connection
Some processes should not be killed just because the terminal went away
In the old days, you would do
nohup some-long-running-command > output
Then if your telephone call was cut off, the command would continue to execute
Most shells have this built into the & operator these days