Cumulative Update 16 includes all application and platform hotfixes and regulatory features that have been released for Microsoft Dynamics NAV 2015.
For information about how to install the cumulative update, see How to Install a Microsoft Dynamics NAV 2015 Cumulative Update.
For information about how to work around a recent process change, see How to Get Back the ‘Hotfix Directories’ from NAV 2015 Cumulative Update 1.
For a list of all cumulative updates for this version, see Released Cumulative Updates for Microsoft Dynamics NAV 2015.
You can check for complete details here : https://blogs.msdn.microsoft.com/nav/2016/02/05/cumulative-update-16-for-microsoft-dynamics-nav-2015-has-been-released/