A click farm is a business that pays employees to click on website elements to artificially boost the status of a client's website or a product.
Click farms are usually based in developing countries, where wages are extremely low by Western standards. Workers typically make a dollar or two per thousand clicks, perhaps as little as $120 a year.
Click farming is extremely common on Facebook, where the clicks are often to the site's Like button. Page owners can buy Likes directly from click farm operators -- many of whom have Facebook pages -- or they can increase the number of Likes their pages get by paying for ads.
When Likes are purchased directly, a large number of click farm workers are told to click the Like button for the page. When the page owner purchases an ad to promote the page, the ad appears on other people's pages. Click farm workers also click such links as a normal part of their jobs so that their targeted clicking for purchased Likes is less easily tracked.
See a video about click farming on Facebook:
See also: click fraud