Root

In Windows servers, there is typically a user named "Administrator" which has all the privileges to make any changes on the system. The Linux equivalent to this is the root user. You can login to the terminal as the root user directly with the username root, and the root password. Keep in mind, that with great power comes great responsibility. Linux systems will typically not prevent a root user from running the command 

[root@localhost ~]$ rm -rf /*

This will delete all data on your system.

It is typically recommended to do most of your work as an unprivileged user, and just use root privileges when you need to make a system wide change, like installing a package or something.

Some Linux distributions, like Ubuntu for instance, will try to limit the ability to login directly as root as a security measure. There is fortunately an easy way for you to access root privileges without having to logout of your user account and login as root. This is in the next section.