knowledge check

A skill check used to remember a useful bit of information in a particular field of knowledge. Arcana, Dungeoneering, History, Nature, and Religion are the skills most commonly used to make knowledge checks.
    Refer to these rules whenever a creature is making a knowledge check, regardless of the skill it is using.
         Action: No action. A creature either knows or doesn’t know the information.
         DC: See the Knowledge Checks table. The check DC increases based on the topic and how common the knowledge is. A Dungeon Master might decide that certain information is available only to creatures that have training in the appropriate knowledge skill.
         Success: The creature recalls a relevant piece of lore in the field of knowledge or recognizes a clue related to it.
         Failure: The creature doesn’t recall any pertinent information. The Dungeon Master might allow a new check if further information comes to light.

InformationDC
GeneralEasy
SpecializedModerate
EsotericHard

Published in Rules Compendium, page(s) 313, 129.