If you are running X:
Otherwise I think this might be the text interface but I'm not sure:
About the RC directories.
The S scripts mean they will be started at that runlevel.
These scripts run when you shutdown your computer.
The numbers are just the order in which the startup and kill scripts run. So a script with a lower number will run before a scripts with a higher number. For instance you want to up your iptables before you startup the rest of your networking. And vice versa, shutdown the networking services before shutting down your iptables.
To read more about the booting proces: