Unlike with a foreground process, the shell does not have to wait for a background process to end before it can run more processes.

Within the limit of the amount of memory available, you can enter many background commands one after another. To run a command as a background process, type the command and add a space and an ampersand to the end of the command. For example:

Immediately after entering the above command, the shell will execute the command. While that is running in the background, the shell prompt (% for the C Shell, and $ for the Bourne Shell and the Korn Shell) will return. At this point, you can enter another command for either foreground or background process. Background jobs are run at a lower priority to the foreground jobs.

You will see a message on the screen when a background process is finished running.