As far as I can tell, there is no documentation, either on-line within the installer or in the printed documentation that comes with RedHat 6.1, explaining what the various package groups are. They are not all intuitive. For example, what exactly is in "DOS/Windows Connectivity" or "Network Management Workstation"? Ideally, there would be a description associated with each package group, displayed when that group is clicked on by the user, similar to the descriptions of the indivdual components if you click "Select individual components" (or something like that) on the package group page. Even if that's not possible, at least the documentation should list the various package groups and what they're for.
The description of each individual package in included in the Reference Guide for Red Hat Linux 6.1. This guide is available both in print (with the boxed set) as well as online at the Red Hat website. Included with this is a brief synopsis of the package groups which exist. These same individual package descriptions are available in the GUI Individual Package Selection and will appear at the bottom of the screen with each package which is selected. In previous versions of Red Hat Linux, pressing the F1 key when an individual package is highlighted would provide the same information, but we let a bug slip past and that feature is not available in release 6.1. Look for it to return in future releases. We will also put together better documentation about the Package Groups which exist in Red Hat Linux.