Ubuntu does not provide these codecs and drivers out of the box because they
are restricted and illegal to install in some countries. Mp3 is owned by a
German company and it is copyrighted. CSS that is required to play
commercial DVDs is similarly protected by copyright. Some distributions do
not care and provide them without any thought to the morality or legality.
Ubuntu places the responsibility on the user.

In Synaptic search (not quick search) for restricted-extras and install the
ones for Ubuntu. They are all packaged together. While you are there install
VLC. It will allow you to play DVDs and it comes with many of its own
codecs. However, if you install the ubuntu-restricted-extras you should be
able to play them with Totem or any other player.

You can do the same thing from a terminal. Just type: sudo apt-get install
ubuntu-restricted-extras and press Enter. You will have to provide your
password. After they are installed keep the terminal open and install VLC
with sudo apt-get install vlc