As there is much confusion about the official repositories, this wiki tries to explain their meaning:
The current repository can be found in current/os/i686 or current/os/x86_64 on your favorite mirror. It contains Arch core packages and some additional software, the philosophy is "one of each", so that it should contain one editor, one window manager and so on (of course, that philosophy isn't followed too strictly. Snapshots of the current repository are also published on the full installation cd.
The extra repository can be found in extra/os/i686 or extra/os/x86_64 on your favorite mirror. It contains all Arch packages that didn't make it into current. Important things like kde or gnome can be found here.
The unstable repository can be found in unstable/os/i686 on your favorite mirror. This repository contains experimental and unstable software. For example, there are some experimental kernel drivers or -svn versions. Contrary to popular belief, it is perfectly safe to enable the unstable repository, as there are no name collisions with current or extra, this means that packages from unstable are only installed if you explicitly to do. The unstable repository is currently not maintained for x86_64.
The community repository can be found in community/os/i686 or community/os/x86_64 on your favorite mirror. It is maintained by the Trusted Users (TUs) and is part of the Aur User Repository (AUR). It contains packages from the AUR that have enough votes and were adopted by a TU. The community repository has only recently become available for x86_64, so don't expect to find many packages in there.
The testing repository can be found in testing/os/i686 on your favorite mirror. testing is special. It contains packages that are candidates for the current, extra or unstable repositories. New packages go into testing if:
- they are expected to break something on update and need to be tested first
- they require other packages to be rebuilt. In this case, all packages that need to be rebuilt are put into testing first and when all rebuilds are done, they are moved back to the other repositories.
testing is the only repository that can have name collisions with any of the other official repositories. If enabled, it has to be the first repo listed in your pacman.conf file.