[CentOS] RH Server/Client disk sets -> Centos; how?

I'm running Centos on 12 machines.

Colleague runs Redhat Enterprise Linux and while studying his system,
I see some gibberish/complication about his system being a "Client"
install, not a "Server" install.  Apparently, RH provides completely
different disk sets for Server and Client installs. I've gone to the
RH website and read about the difference between Client and Server,
but I still don't understand why they make 2 different disks.  In the
"old days" of RH, there would be 1 set of disks, and when the install
began, you would choose "server" or "workstation" as a way of choosing
a default set of packages, and then you could freely pick and choose
additional things.  You could install gnome on a server, or an http
server on a client.

Centos seems to follow the good old RH packaging approach.

This RHEL Client/Server thing actually causes some wrinkles if you try
to transition a running system from RH to Centos, because the
repository names are different.  RH will have a version name like
"5client" whereas Centos will just have 5.

I understand this Centos list is not quite the right place to ask "why
does RedHat do that?", but I bet some of you will know.

What I really want to ask here is: what is the relationship between
the several RHEL install types and the Centos disks? Does Centos
collect up all the SRPM/RPM packages from both RHEL Client and Server?

-- 
Paul E. Johnson
Professor, Political Science
1541 Lilac Lane, Room 504
University of Kansas