To expand on BrianMcGee's post;
There are other posts around that go into this in more detail (eg
http://www.linuxquestions.org/questi...estion-622512/), but basically:
1. RHEL is NOT free, except for the (30 day?) eval version. You pay, you get an install num which gives you access to the RHEL update system and various forms of support, depending on how much you paid. long support cycle (5 yrs?)
2. Centos is a free copy of RHEL, sans RH logos and support.
3. Fedora is totally free SW only (does not inc proprietary codecs), sans support. Short upgrade cycle (every 12 mths?)
bleeding edge, so not recommended for production systems.
If you look around on LQ, it is possible to get the proprietary codecs/audio-visual drivers you need eg Mplayer etc.
HTH