[CentOS] New to Centos and have question about updating packages

I have been using Freebsd for along time. I have a client of mine that  
wants me to use Centos for his email server and web server. Anyway  
with Freebsd to update the packages file you use the following commands.
portsnap fetch fetches all the current port trees
portsnap update adds all the new ports to the tree on the server
portupgrade -arR will install all the ports that are installed on the  
server.
  Now my question is what are the commands for Centos to fetch ,update  
and install, all the packages installed on the server. I would like to  
use Yum. Any help would be great.

Thanks

Darrell Betts
betts at norden1.com
-----------------------------------------------------------
Looks like I Picked the Wrong Week to Stop Sniffing Glue.
-- Steve McCroskey --

Live ATC Feed from Toledo Express Airport http://audio.liveatc.net:8012/ktol.m3u