A web page that is nothing more than a page of links to other sites. These destination sites have been set up purely to provide a link and provide users with no real value. Caution should be taken when subscribing to link farms. Google identifies most link farms as spam.
Web sites designed and specifically used for the purpose of maintaining links between sites mainly for ranking purposes. Link Farms are penalized by most of the search engines.
Web sites designed with the sole purpose of linking member sites to each other and because the links are required, search engine place little value on the pages.
sites created and maintained solely for the purpose of constructing links between member sites. Should be avoided as a violation of most search engines' policies; their use won't build your site's link popularity, and may result in a ranking penalty.
Link farms are Web sites that have hundreds (and sometimes thousands) of outgoing links. These links are useless and sometimes can be even worse that usless. Google and other search engines can ban you if you are involved in link farms.
Free For All link sites which exist for the sole purpose of increasing the site rankings for their members. Not recommended unless you want your site banned - best to use traditional search engine optimisation strategies.
Pages that consists of little else but links to other sites and usually the sites listed have links back to the farm page. The goal of a link farm is to artificially boost rankings through link popularity and is consequently at risk of penalty or ban.
These are web pages that consist only of links to other sites. They exist in an attempt to gain link popularity and therefore an increase in search engine ranking. However, most search engines punish sites that use this tactic by lowering their place on the results pages.