They're two different Linux distributions. Google fill find you their respective homepages, but these can be somewhat overwhelming. I find a good place to start on distributions is DistroWatch. The DistroWatch summary pages you might be interested in... TurboLinux and RedHat. If you're not a commercial user you may want to look up The Fedora Project, the community RedHat distro.
--Tim [ April 15, 2004: Message edited by: Tim West ]