So old versions of Ubuntu are unsupported. What does that mean?
It means that you won't get security updates and selected high-impact bug fixes any longer.
You can continue using your Ubuntu, without security updated and bug fixes, as @htorque said.
I would to add that you can also install new software available in the frozen repositories, simply substituting the server you are using in
sources.list with the following
Needless to say, you are strongly advised to upgrade to a newer release of Ubuntu.