You can use client control add-ins to add custom functionality to Microsoft Dynamics NAV Role Centers and pages. The extensibility framework has changed with Microsoft Dynamics NAV 2013 R2 and it is now possible to develop control add-ins that can be used on any display target.
Add-ins that are developed with Microsoft Dynamics NAV 2013 are still supported and displayed on a Microsoft Dynamics NAV Windows client only. Using that framework you can continue to write add-ins for the Microsoft Dynamics NAV Windows client. Using the new framework in Microsoft Dynamics NAV 2013 R2, you can write add-ins that can be run from any client.