The Knowledge Domain encompasses mortal knowledge, drawing information from mortal minds to the one who controls the domain. Often this domain manifests itself by the god directly observing the world -- the spores of Ueberroth, the weather of Tzu'misel, or the elements of Defluo -- but not always.
This domain is in direct contrast to the Secrets domain. Only divine knowledge and that which is cloaked in secrecy exist outside of the Knowledge domain.
Mortals seeking information oftentimes pray to one of the gods of knowledge.