Can you explains the basic difference between CentOS and RHEL?
CentOS Linux is based on the source code of Red Hat Enterprise Linux. However, due to legal issues CentOS can not use Redhat or RHEL trademarked name on their site or on DVD media. CentOS now refers to Red Hat as the "Upstream Vendor" and a "Prominent North American Enterprise Linux Vendor.
CentOS has numerous advantages over some of the other clone projects including: an active and growing user community, quickly rebuilt, tested, and QA'ed errata packages
CentOS does not provides the RHN style support. It depends upon community mailing lists, forums and 3rd party sites to provide support. CentOS Linux is free but do not get any commercial support or consulting services from Red Hat and lack any software, hardware or security certifications. Also, the CentOS do not get access to Red Hat services like Red Hat Network. If you need access to RHN or support service go for Redhat otherwise CentOS will help you.