You're having a perspective issue, not to worry.

From the Linux / Ubuntu perspective yes either one can be root. Sudo means
"superuser does" and was first seen in SCO UNIX, and from our frame of mind we
are logged in always as a user and never "Root", so to get stuff done we must
become Root to administer the system.

In large UNIX shops you will find that most system admin's are logged in as
Root and never as a user. So, when Butthead Bob or Winning Willie are your line
telling you that the system isn't reponding, you the SysAdmin, must be able to
take on their identity in the system. That is where the command su winniewillie
will let you login in has him. He then can take you threw the exact same steps
that created his problem. Most of which were waking up that morning.