We've looked at one way to get superuser access using the sudo command. You can also run commands as the superuser with the su command. This command will "substitute users" and open a root shell if no username is specified. You can use this command to substitute to any user as long as you know the password.
There are some downsides to using this method: it's much easier to make a critical mistake running everything in root, you won't have records of the commands you use to change system configurations, etc. Basically, if you need to run commands as the superuser, just stick to sudo.
Now that you know what commands to run as the superuser, the question is how do you know who has access to do that? The system doesn't let every single Joe Schmoe run commands as the superuser, so how does it know? There is a file called the /etc/sudoers file, this file lists users who can run sudo. You can edit this file with the visudo command.
Open up the /etc/sudoers file and see what superuser permissions other users on the machine have.
What file shows the users who have access to sudo?