Poking around the web looking into the basics of SEO (search engine optimization) you'll soon discover many articles professing to give the basics of SEO. After reading a few of these page you should soon notice something interesting, they all cover the same basic points AND they cover the same basic points in the same order.
If you know how to do a little behind the scenes prodding, you'll discovered that Google has published a pdf file called Search Engine Optimization Starter Guide. This is the source of most if not all of the so-called basic SEO guides on the web.
Do yourself a favor. Before doing any general research on SEO read the Google Search Engine Optimization Starter Guide. Since they are the original source of this document you can get it straight from the horse's mouth -- so to speak. And, when you do further research you will be better prepared to identify new information.