The knowledge base (Docs link at the top of topic listings) is a way of showing a specific subset of topics that are designed for documentation purposes.
This is done by tagging a topic with the knowledge-base, and then the topic is automatically added to the docs.
This isn’t clear to all users, so I’ve created a tag group for Docs and restricted use of that tag to Trust Level 4, so new users aren’t confused and add that tag by mistake.