Reciprocal Link: In some cases, co-citations and other links will be mutual across pages -- so two sites may link to one another frequently, but not deliberately. However, in some cases, reciprocal links are created in order to create a false sense of authority for a webpage in order to manipulate search engine results.
Some methods that pages use to create reciprocal links include various low-quality link schemes such as trading links or using three-way link trades. These trades tend to produce links that do not have similar topics as one another; these links may also be placed deep within a website, so they do not have any real authority. This practice is associated with black hat SEO tactics and is similar to the link directories of the internet's past.
Reciprocal link exchanges often hurt websites far more than they help when it comes to ranking high in search engine results. Google and other search engines may look at the quality of links leading to your webpage and the quality of sites that your page links to. If there are too many that come from low quality websites, your site can actually be penalized in the rankings. However, more natural links, such as those that cite your page in editorial content, are more likely to be given authority than those that appear in directories or other link schemes.