If you are still running Ubuntu 16.10, which was released last October, it’s time to upgrade. Also known as "Yakkety Yak", it was released on October 13, 2016, and as per short-term release lifespans, has petered out its nine-month support cycle. If you’re still running 16.10, then it’s time to upgrade to Ubuntu 17.04 which will be supported until the start of 2018.
Once a release, such as Ubuntu 16.10, reaches its end of life, it no longer receives any maintenance updates, critical security patches, or updated packages. The long-term support releases are better suited for people who don’t enjoy upgrading their system every six to nine months.
The current long-term support release is Ubuntu 16.04, which will continue to receive updates until spring 2021. In the meantime, Ubuntu 18.04 LTS will be released in April 2018; that release will be given life until April 2023.
In order to find out the support status of your system, open the terminal and type: ubuntu-support-status. If you’re on an unsupported release you should be able to open the update manager and be offered an upgrade to a newer version. Doing system upgrades on Ubuntu is usually problem-free, but depending on how much tinkering you’ve done to your system, you may experience problems.
Source: OMG Ubuntu