A link farm on the World Wide Web, is any group of sites that all hyperlink to every other website in the group to increase search engine optimization. In theory, the more websites that link to yours, the higher your ranking in the search engine results will be because the more links indicate a higher level of popularity among online users. However, search engines like Google consider link farming as a form of spam and have been implementing procedures to banish websites that participate in link farming, so the term link farming has garnered negative connotations across the Internet.
Some link farms can be created by hand, but most are created through automated programs as well as services. A link farm is a form of spamming the index of a search engine (sometimes called spamexing or spamdexing). Other link exchange systems are designed to allow individual websites to selectively exchange links with other relevant websites and these systems are not considered a form of spamdexing.
Users should be aware of the repercussions of this action as the major search engines penalize websites that participate in link farming, thereby reversing their intended effect. A link farm is a Web page that is nothing more than a page of links to other sites.
In Unix systems, a link farm is a directory tree containing links to files in a master directory tree of files.