What is 'sudo tar -xzf'? Why it is used?

tar is basically The GNU version of the tar archiving utility for more information on tar go to the terminal and type man tar.

You will find out what exactly xzf is used for. Basically they flags (options) when you run a tar command.

[-]x --extract --get:
-z --gzip:
-f --file F:

The order of this command does matter though.

Basically your command

sudo tar -xzf utorrent-server-3.0-ubuntu-10.10-27079.tar.gz

will extract the tar.gz archive that you specify as (utorrent-server-3.0-ubuntu-10.10-27079.tar.gz) as root privileges.

tar is the Swiss army knife of extracting archives. It can handle many different archives, such as tar.gz, tar.xz, tar.bz, tar.bz2, tar.lz...

Your command contains the following three options:

• -x = extract
• -z = gzipped archive
• -f = get from a file, not a tape drive

To find more help on tar, enter tar --help or man tar in your terminal.

So your command extracts the archive utorrent-server-3.0-ubuntu-10.10-27079.tar.gz to a directory. It does not install the utorrent server, unlike dpkg -i or sudo apt-get install.

tar archives for programs typically contain Linux binaries, which you can run with './ binary-name'.