When you use "su -" you create a new shell started by that user for working in.
There aren't any programs executed by a normal su but you can use su to run a program as another user like:
su - -c "iptables -L"
In this case you would get the iptables rule listing.
Edit: perhaps this is a better example:
su root -c "/sbin/iptables -L"
Last edited by david_ross; 04-22-2003 at 05:11 PM.