Cumulative Update includes all application and platform hotfixes and regulatory features that have been released for Microsoft Dynamics NAV.
NAV 2018 :- Cumulative Update 08 for Microsoft Dynamics NAV 2018
NAV 2017 :- Cumulative Update 21 for Microsoft Dynamics NAV 2017
NAV 2016:- Cumulative Update 34 for Microsoft Dynamics NAV 2016