An Encyclopedia is a traditionally a book containing a collection of information on almost all topics ordered by the words describing the items. It describes persons, places, products, companies, peoples, and much more. A traditional Encyclopedia occupies about one meter of shelf space.
When the computers become more and more common Encyclopedias is by their structure of words and cross references extremely well suited for moving the contents from the book format to the computer format. Firstly because it is a lot easier to carry around and find what you are looking for and secondly because it is possible to include sounds and films as illustrations.
These Encyclopedias are available to look at using the Internet:
[Wikipedia] -- [Nupedia] -- [Britannica] -- [Encarta] -- [Columbia Concise]