There are a number of different builds of the Debian-Installer CD images that serve different purposes.
The most important build is the current official release, currently included in Debian 6.0. These images are static and unchanging, and are the ones mostly likely to work for most people. While testing of these images is still useful, most problems with them are well known by the team within a few weeks of their release. See the errata page for the worst of the known issues.
The other most commonly used builds are the daily builds. These are newer images that need testing in the hopes of one day becoming an official release. They are just a link to one of the two types of images described below; which one is linked to depends on where we are in our release cycle. Installation reports using these images are very valuable to us.
The sid_d-i images are new CD images produced each day. These images use the version of the installer from the unstable distribution, although they still install the testing distribution. Typically the daily CD build links point at these images.
The jessie_d-i images are also produced each day. They use the version of the installer from testing, and install testing. At release time, one of these images is picked and becomes the official release image. Near a release the links to daily CD builds will be switched to point to these images, so that they can get testing.
The weekly full CD and DVD builds take several days to build, so are only regenerated once per week. The version of the installer on these varies, but is generally the version we want to get tested at the current time.
All the other Debian-Installer images, including netboot,
are collectively known as the
initrd images. Again several different
builds are used.
As with the CD images, the most important initrd build is the current official release.
The other most commonly used initrd builds are the daily builds. These images are built approximately once each day by some Debian-Installer developers, typically on their own personal machines. They always include the latest version of the installer, from the unstable distribution.
From time to time an official Debian-Installer initrd build will be done, as part of a release of the debian-installer package. These images are built on the Debian autobuilder network like any other package, and are placed in the dists/unstable/main/binary-<arch>/current subdirectory.
When Debian-Installer is released, one of these official builds is copied to the dists/testing/main/binary-<arch>/current subdirectory.
Build status page
The status of all of the periodically built images is tracked and collected on the build status page. This page can't tell if the images work, only if it was successfully built.