sudo

It means "super user do" and you must use it every time when you try to do an action that only SuperUser can do. For example:

If you want to install some packages, you must do:

sudo apt-get install package1 package2 ...etc.

But you can do something better:

sudo passwd >>> with this you will create a password for the root user and then you can log in this way:

                  anakron@udec:~$ su root
                  Contraseña:
                  root@udec:/home/anakron#

And now you can do Everything that you want without use any sudo.

Bye!

Actually, you don't need to create a password for root, you can simply type

sudo su

enter your normal user password and then you have a shell in which you are the root (Administrator).

You said "I am a newbie so I don't understand a lot about Linux" ...

I suggest you:
Is strongly suggested to do not login as root, or get access to root user, to use Ubuntu and generally all Linux.

Simply when a command need root privileges simply use sudo. for example:

sudo apt-get update
sudo apt-get update

Sudo ask you for a password so give your user password, you don't see nothing when you type it, then press enter.

Hope this helps