Definition:
A link farm is a website, or a group of websites, created with the sole purpose of increasing the popularity of links from another site, increasing the number of incoming links. A link farm usually looks like a regular web page, but most of the content is made up of hyperlinks, often random and unrelated, from other websites.
Link farms can be advertised as services for building content. They are often established by creating a network, which has often been created for the sole purpose of gathering a series of addresses to point to a website. Because Google doesn’t like links between unrelated sites, some of these link farms divide their links into categories or a directory.
Evolution of link farms
Link farms originated in response to Google’s ranking algorithm, PageRank. PageRank thinks of links as votes, where a link from one page to another page is considered a vote, so pages with the most links are considered valuable. Link farms were created to help increase PageRank, but nevertheless, in recent times, Google and other search engines have adapted their algorithms to prevent link farms from appearing at the top of search engine page results (SERPs).
Link farms and Black Hat SEO
There are many service providers that promise to help increase the popularity of links, through link exchange programs, often linking a page with websites that have nothing to do with their content. But users should be aware of the consequences of this action, as the desired effect may be being reversed. A link farm is a web page that is nothing more than a page of links to other sites.
If a website is found to have created link farms, it can be penalized by Google and other search engines, as these are considered a method of “black hat”of search engine optimization (SEO), as the content of websites that link together is often unrelated, was not created by a human being (as it can be created using programs or services) and is often of a very low quality. Search engines can detect link farms with ease and these should not be seen as a legitimate long-term search optimization strategy.