When you logged in to ubuntu Linux ssh concole you getting:
25 packages can be updated.
60 updates are security updates.

Ubuntu Linux can be upgraded using GUI tools or using traditional command line tools such as: 

  1. apt-get command - apt-get is the command-line tool for handling packages.
  2. aptitude command - aptitude is a text-based interface to the Debian GNU/Linux package system including Ubuntu Linux

I prefer to install updates via apt-get command line:

1. gpt-get update : Update is used to resynchronize the package index files from their sources via Internet.
2. apt-get upgrade : Upgrade is used to install the newest versions of all packages currently installed on the system
3. apt-get dist-upgrade : Install kernel updates on a Ubuntu LTS server
4. reboot

For Server Version upgrade from LTS to LTS:

sudo do-release-upgrade

NOTE: Please always make sure you test the target LTS you're being prompted to upgrade to in a LiveCD on the machine you're using to make sure everything works properly before going in for the real upgrade itself.