ok, firstly you should read the 'man' pages on any command you are having difficulty with:
Code:
dave@dave-laptop:~$ man shutdown
Scroll through the man page using the return key, and quit using the q key.
Secondly, a quick answer to your problem, use the following:
Code:
dave@dave-laptop:~$ shutdown -h now
From reading the man page, you will realise that the shutdown command must be given a time at which to enter runlevel 0, and commence shutdown. It does not start immediately, since that would not allow the system to instruct users to logoff.