Shucks, I'll give it a shot.
A basic FreeBSD install doesn't require a graphical environment. (Neither does a basic Ubuntu install, depending upon your proposed use of it.)
If you want to watch movies, browse many websites, use some kind of Office like software, etc., you will probably want a graphical environment.
The fact that something doesn't have a graphic environment doesn't mean it's a server, nor does it being a server mean that it can't have a graphical environment.
A server, as its name indicates, serves. It may serve files, it might be a web server, it might run some kind of database. It can do this and have a graphical environment though that's probably not typical.
So, the short answer is that the server can have the graphical environment, though it's not typical. In FreeBSD, generally one starts with a small install, that could be easily used as a server, then decides what programs to install.