Ever run a long operation in a terminal on Linux? You don't want to have to keep checking back to see if the operation has completed, but you don't want to waste time letting the session sit idle after completion. To make Linux ring the terminal bell, thus alerting you when your job is complete, you can use the echo command.

echo -e "\a"

In context, you would most likely do something like this:

tar cvj /homes.tbz /home && echo -e "\a"