Its a group of massive links of different websites, it is mostly seen on a page called partners etc... Google hate this type of linking so i suggest just follow their rules. just a precaution to prevent any problems it can bring.
Link farming is number of website group that is use to obtain backlinks on our targeted website. Search engine mostly consider it as form of sapping, so it is unethical technique and know as black hat SEO technique.
Link farm is a bad technique which uses to increase huge number of back links to website. It is a spam technique.
For more info on link farm check this link Link farm - Wikipedia, the free encyclopedia
Link Farming is process of link exchange like group of website which links to each other in group for increasing search engine optimization. Some of the websites in link farm used to have same content as well. It is illegal or Back Heat technique of search engine optimization for build up ranking in short time which can be detected easily by search engine.
Link Farming
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