Over the past year or so Microsoft has changed the branding of Microsoft Dynamics NAV in the cloud so you might well be confused.
Here is my understanding from a slide shown at Directions EMEA in Oct 2017. Note that "Tenerife" is a code name pending formal annoucement of a product name.
|End 2016||Dynamics 365 for Financials, Business Edition||Dynamics NAV 2016|
|Spring 2017||Dynamics 365 for Finance and Operations, Business Edition||Dynamics NAV 2017|
|Fall 2017||Dynamics 365 for Finance and Operations, Business Edition||Dynamics NAV 2018|
|Spring 2018||Dynamics 365 "Tenerife"||Dynamics NAV 2018 R2|
|Ongoing||Dynamics 365 "Tenerife"||
Dynamics 365 "Tenerife"