The sleep command simply waits a set amount of time. The given time specification can be an integer (meaning seconds) or an integer followed by the letter s (also seconds), m (minutes), h (hours), or d (days).

$ sleep 5m              Do nothing for 5 minutes

sleep is useful for delaying a command for a set amount of time:

$ sleep 10 && echo 'Ten seconds have passed.'
(10 seconds pass)
Ten seconds have passed.