[CentOS] What is in a yum group

I want to install Xfce on a ClearOS server.  They have not defined any 
desktop groups (actually no groups other than minimal).  But lots of 
Xfce rpms are in their repos.

How can I see what rpms Centos would install with a 'yum group install'?

Then I get to install vnc server and set up the client right...

thanks