what does mean sudo -i command

Before I describe about this you should know about sudo command..

The sudo command    <------ about="" click="" it.="" know="" link="" nbsp="" on="" p="" please="" this="" to="">
If you run a command "man sudo" in shall your console its tells you what -i does .. you can see bellow info there..

-i [command]
                   The -i (simulate initial login) option runs the shell specified in the passwd(5) entry of the target user as a login shell.  This means that login-specific resource files such as .profile or .login will be read by the shell.  If a command is specified, it is passed to the shell for execution.  Otherwise, an interactive shell is executed.  sudo attempts to change to that user's home directory before running the shell.  It also initializes the environment, leaving DISPLAY and TERM unchanged, setting HOME, SHELL, USER, LOGNAME, and PATH, as well as the contents of /etc/environment on Linux and AIX systems.  All other environment variables are removed. 

So when you enter "sudo -i" command and if you have sudo access then by using you sudo privilege the command will change you from normal user to Administrator. After that command you can see your self as root. It will not ask you root password as its user sudo authentication to get you there.

Pritam... :)