Internal links are hyperlinks from one page of a website to another page of the same website, keeping the URL address internal. For SEO marketers, internal links are important as they are a signpost to Google’s ranking algorithms. The text highlighted within the hyperlink should therefore be highly relevant to the destination page.
While using internal links will not affect the rank of pages against other websites, it’s a signpost to Google that the page being directed to is the authoritative resource for the keyword highlighted by the hyperlink. As such, internal links are used to show which pages of websites deal with which keyword queries.
To prevent an internal link from being interpreted in this way, webmasters must add a rel=nofollow attribute to the link.