Fedora repositories are included in the fedora-release package. The actual .repo files included are:

/etc/yum.repos.d/fedora.repo
/etc/yum.repos.d/fedora-updates.repo
/etc/yum.repos.d/fedora-updates-testing.repo

fedora.repo defines the following three repositories:

fedora-updates.repo defines the following three repositories:

fedora-updates-testing.repo defines the following three repositories:

From these nine repositories, by default are enabled:

The rest are disabled and they are used by developers, programmers and testers to improve existing programs in these repositories.

In particular it is interesting that you enable [updates-testing] if you wish to support the task of testing new programs being published in Fedora. The [updates-testing] repository is a precursor to the repository [updates] where the packages are considered stable and are declared so to alert users that they may have minor problems. If you have a Fedora FAS account, then you can vote and give a positive or negative karma according to your experience with the new program under testing in bodhi.

For Fedora developers there is an additional package that adds another .repo file with Fedora repositories, /etc/yum.repos.d/fedora-rawhide.repo, also known as rawhide.

$ su -c "yum install fedora-release-rawhide"

Install fedora-release-rawhide only if you know what you are doing, never leave this repository enabled by default if you are newbie, in this repository is where Fedora development occurs and there are versions that are not even guaranteed to work. By default all rawhide repositories are disabled when you install the package fedora-release-rawhide.

fedora-rawhide.repo defines the following three repositories: