Software Sources Listing

While exploring my new RHEL6 Server install (I am trying to learn it in preparation for taking the RH certifications at some point) I was looking through the Software Sources list in the Add/Remove software GUI. I noticed that I do not have check marks next to "Red Hat Enterprise Linux 6.1" but have checkmarks for RHN tools and RHEL Server (v. 6) I am just curious what the 6.1 line is for? I've tried checking it, but it doesn't stick. I presume this is because in my entitlements list the channel for my system is listed as the RHEL Server (v. 6).

Any clarification would be greatly appreciated!

Also, are there other channels/sources that the Desktop/Workstation varients get access to? I am wondering what differences a Desktop installation would have, other than not gaining access to server-related packages. Red Hat's comparison chart is rather lacking of any information at all.