clipped from: www.therealtraffic.com   

A. A set of web pages that have been built for the sole purpose of increasing
the number of incoming links to a web site. This is done in order to increase
link popularity and search engine rankings. Link farms usually require a reciprocal
link from sites seeking listings. Link farms are a known spam tactic and sites
that participate in them are likely to be penalized or banned from the major search
engines.