SEO consists of optimizing your content online, so that a search engine such as google prefers to show it as one of the first results for searches of a certain keyword. That is to position your website in the list of Google or other search engines in the Top 10. Positioning is crucial because when we look for something in particular to do it comes a lot of results in the search engine and most people do not pass the first page so if your website comes out on the second page you will hardly receive visitors, therefore SEO is a part of digital marketing.
Your post, article or product with a link to any other page of the Google search results that is not the first, is the same as not being positioned at all.
But to understand how to appear in the first place in search results pages, you first have to know how search engines work.
To know more I recommend that you take this SEO courses so that you will become an expert in the SEO world