Yum is the application installer used by RedHat. It connects to various known repos to download requested software. To create a YUM repo simply drop all your rpm files into a directory on a web server and inform the RedHat system you wish to install them on by creating a file in /etc/yum.repos.d
The file should be called something.repo and the format follows the following:
name=My YUM repo baseurl=http://10.0.0.1/redhat5/myrpms/ enabled=1 gpgcheck=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
The gpgkey entry details a file with gpg auth details for the rpms in the repo, however, this will be disabled if gpgcheck is set to '0'.