Background Commands with ampersand - &

To background a command simply add an ampersand (&) on the end.

Reference:
UNIX for beginners
http://people.cryst.bbk.ac.uk/~tickle/notes/unix-beg.html

If a command is terminated by the control operator ampersand (&), the shell executes the command asynchronously -- that is, the shell does not wait for the command to finish before executing the next command.
The format for running a command in background is:

command1 & [command2 & ...]

If the shell is not interactive, the standard input of an asynchronous command is set to /dev/null

Reference:
Linux / Unix Command: ash
http://linux.about.com/library/cmd/blcmdl1_ash.htm