Fedora's Extra Packages for Enterprise Linux (EPEL) repository provides the ability to install software packages which are not included in the official CentOS or Red Hat Enterprise Linux (RHEL) repositories.
EPEL is not maintained by Red Hat, and is a volunteer effort from the Fedora Community. Although it is a well maintained repository, there aren't any commercial support contracts for software held within it.
Shown below is information from the Fedora Wiki regarding the differences between EPEL and other third-party repositories.
How is EPEL different from other third party repositories for RHEL and derivatives?
EPEL packages are in most cases built or derived from the equivalent ones in Fedora repository and maintained by the same people. It has also been improved through peer reviews, testing and feedback from end users.
EPEL adheres to the well documented Fedora Packaging guidelines, which RHEL has started following. This ensures good integration.
EPEL is purely a complementary add-on repository and does not replace packages in RHEL or layered products.
EPEL has a large team of contributors including Red Hat engineers and volunteer community members working together to maintain the repository.
EPEL only provides free and open source software unencumbered by patents or any legal issues.
The "CentOS Extras" repository includes a package to install EPEL, and is enabled by default. To install the EPEL package, run the following command.
sudo yum install epel-release
If this fails, the additional CentOS Extras repository may be disabled. Proceed to the next section to install the repository manually.
wget http://dl.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm sudo rpm -Uvh epel-release-5*.rpm
wget http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm sudo rpm -Uvh epel-release-6*.rpm
wget http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-5.noarch.rpm sudo rpm -Uvh epel-release-7*.rpm