A reference work is a compendium of information, usually of a specific type, compiled for ease of reference. That is, the information is intended to be quickly found when needed.
The writing style used in these works is informative; the authors avoid use of the first person, and emphasize facts. Indexes are commonly provided in many types of reference work. Most are updated as needed, typically with a new edition each year.
In libraries, the most recent edition of most reference works may not be taken out of the building, or even out of the reference area of the building, although duplicate copies or earlier editions may be allowed to be borrowed.
Examples of reference works:
See also: Wikipedia's list of reference tables