The document discusses search engine optimization (SEO) and how it works. It explains that SEO is the process of affecting how visible a website or webpage is in unpaid search engine results. It then outlines the different types of SEO, including on-page SEO which involves optimizing website content, and off-page SEO which refers to link building and other external techniques. The document also discusses important SEO building blocks like keywords, links, and crawlers. Finally, it defines white hat SEO which follows search engine rules, and black hat SEO which uses unethical tactics.