Internal links are links within a website that take a user from one page to another page. They are found in the content of your site and provide valuable signals to search engines about where to find content, both on your own website – and throughout the web. Not only do internal links allow users to easily navigate a website, and help establish a hierarchical structure, but they can also improve your rankings.
Good internal site links are important for a number of reasons. Search engines need to see content in order for you to rank for it, but they also depend on a solid link structure that is easily crawlable in-order to properly index a website. Building a complete hierarchical link structure and using anchor text links within your website is just one step towards good website optimization.