There are two websites, A and B; A links to website B, and B links to website A. These websites linking to each other are called external links. External links are an important source for getting a website to rank on the top of SERPs. These links are considered a vote by a third party, telling search engines that it is a trustworthy website, carrying quality content.
Internal links, which means a site linking one web page to another web page within the same website, carry less value as compared to external links. External links are created when a website proves its worth, by posting quality content and being popular among users.
Linking Domain
More websites would create external link and cite a website, if they think that the linking domain is trustworthy. If the domain carries viruses or doesnt have an SSL certificate, then other websites would never link back to it.
Popularity
There are websites or web pages that are very popular among users. Some websites believe that if they create external links that are relevant to their own content, and these links take users to the popular website, then it would drive more traffic to their websites. The key here is to post quality articles, and as a way to keep users interested, post another side of the picture or story, as it will make the host website appear to be non-bias discuss.
Relevancy
When the source page finds the target page relevant, then it will create an external link. For example, if the source page is about shoes, and it finds another brand that deals with shoes, posts descriptions and articles about the new fashion trends, then it will create an external link to the target page. When marketers want to create external links, they should always link to those pages that are the closest to what their products are about.
Number Of Links
If a target page has been externally linked multiple times, from different source pages, then a website that wants to create an external link would prefer that target page. If a target page has been externally linked multiple number of times, then this is because the target page contains quality content, and users like reading whats on the page; it could also be due to the relevancy and accuracy of the content.
Relationship Between Source And Target
A source page might link to the target page, because the two brands have some kind of relationship; the brand could be a sub-brand or a franchise of the source page. If the source page wants both brands to be popular among customers, and would want to know the relationship between both brands, then it would link to the target page.
Creating external links give users more content; they also explore a website more to look for other relevant links and content to read. It makes the target page more credible, which is why a source page should also strive to become a target page for another website.