Internal links are an important tool in your SEO strategy. They help not only in the performance of your blog, but also in the user experience. In this case, internal links are all those that link to another page of the same site. All links to pages or articles within the same domain are internal. But if I link to a Wikipedia page, for example, the link in question would already be an external link.
Did you know that Google invites people to test and evaluate search its search engine effectiveness? Yes, we talk a lot about Google bots, but it is important to remember that there are also human beings evaluating how the platform works.
A friendly URL is the address or path that will lead the user to a particular page to check the content he/she wants. This path should be clearly defined, always thinking in technical SEO terms and user experience.