Although it sounds a lot like bureaucracy, it is the [http://www.debian.org/doc/debian-policy/ Debian Policy Manual] that makes Debian the best Linux distribution. It describes what packages should contain, how they should be configured, and generally how packages fit together to create a Debian system.
There are policies which govern every package. The most important one is that Debian needs to comply with the FilesystemHierarchyStandard - this makes sure you can always find files where you expect them. There are specific policies which govern which interfaces certain packages follow. For example, every program that sends e-mail needs to Provide: mail-transfer-agent. This means that other programs that need to send e-mail just depend: mail-transfer-agent, and are able to use /usr/sbin/sendmail.
The coolest bit of policy in Debian is the ?MenuPolicy, which ?MandrakeSoft adopted also.
Development
['?PoliciesWhackyIdeas'] This is an ideas pool for future new policies