Question: I used to work in a Ubuntu environment. Machines would be pointed at one of three repos: unstable, testing, or stable. To quote the [Ubuntu FAQ](https://wiki.ubuntu.com/Debian/ForUbuntuDevelopers#What.27s_stable.2C_testing.2C_unstable.3F):

> 
> The “stable” distribution contains the latest officially released
>  distribution of Debian. The “testing” distribution contains packages
>  that haven't been accepted into a “stable” release yet, but they are
>  in the queue for that. The main advantage of using this distribution
>  is that it has more recent versions of software. The “unstable”
>  (codenamed sid) distribution is where active development of Debian
>  occurs. Generally, this distribution is run by developers and those
>  who like to live on the edge.
> 
> 
> 

Even more details are here in the [Debian Release page](http://www.debian.org/releases/).

Now I work in a CentOS environment. Does CentOS use similar names or have an entirely different methodology?

The reason I'm asking is that I want to set up a repo for home-grown packages and I want to have the benefits of unstable/testing/stable but I want to do it in a CentOS-friendly way.

Answer: 
Everything in the default RHEL and CentOS repos is stable. There is the EPEL repo, which is sort of like Universe in Ubuntu and is maintained by the Fedora project. If you want something like unstable/testing you should use Fedora.
There is the RHN [FasTrack](http://www.redhat.com/rhn/rhndetails/fastrack/) channel. I would consider this to be very close in definition to Ubuntu's Testing. It provides packages which are considered production ready, but are slated for release during the next minor update to the OS.

As said in the other answers, this is an enterprise product and does not have a public development (unstable) channel.