What are the update CDs/DVDs?
Update CDs/DVDs are CDs/DVDs which contain all the packages that changed between the zero micro version number (e.g. 5.0.0, 6.0.0, etc.) and a later point release of the current stable distribution. For example, if you already have the full set of debian-6.0.0 CDs/DVDs, you can use the debian-update-6.0.1 CD to turn this debian-6.0.0 set into a debian-6.0.1 set. This type of CD/DVD is intended for vendors having large amounts of pressed zero micro version number CDs/DVDs (which makes them cheaper than individually burned CDs/DVDs). If you order CDs/DVDs from such a vendor, it is possible that you receive CDs/DVDs for a slightly older point release, plus an update CD/DVD for the latest revision. This is a perfectly acceptable way of distributing Debian on CD/DVD. Of course, this type of CD/DVD can also be useful to you as an end user; instead of creating the full set of CDs/DVDs for each new revision of a release, you only need to download and burn update CDs/DVDs for your architecture.