Internal linking refers to linking of one web page to another within the same website. If done strategically, it can help you increase the crawling speed of your website and gain better search rankings in shorter time period.
Internal linking is in the hands of the website owner and is an important on-page SEO component. However, internal linking needs multiple website pages so that you can link them together. As a result, internal linking is a never ending exercise; it keeps on going as long as you publish new content or create new pages.