The ArcGIS Enterprise 10.5 Functionality Matrix whitepaper is now available from here,
FYI: at the 10.5 release, the product "ArcGIS for Server", has been renamed to "ArcGIS Enterprise". The product was re-branded to better reflect the idea that with the software you get "Web GIS" in your own infrastructure. Learn more here.
ArcGIS Enterprise still includes the following components:
- GIS Server (aka, ArcGIS Server)
- Portal for ArcGIS
- ArcGIS Data Store
- ArcGIS Web Adaptor
Hope this helps,