Magento 2.0.18 is the final 2.0.x release. After March 2018, Magento 2.0.x will no longer receive security patches, quality fixes, or documentation updates.
To maintain your site's performance, security, and PCI compliance, upgrade to the latest version of Magento.

Contributing developers—update, reinstall Magento

The following topics apply to you only if you used git clone to install the Magento Open Source GitHub repository. This usually means you contribute code to the Magento Open Source codebase.

If you clone the Magento 2 GitHub repository, you cannot use the Magento software in a production environment. You cannot have a live store that accepts orders and so on.

If you are not a contributing developer, you perform upgrades and upgrades as discussed in Updating the Magento application and components.