The document discusses the importance of search engine optimization (SEO) for marketing. It defines SEO as optimizing a website's architecture and layout to improve search engine rankings and traffic. The key aspects of SEO covered are on-page optimization like keywords, content, and page speed, and off-page optimization like backlinks, social signals, and submissions. Effective SEO requires an understanding of how search engines work by indexing keywords and calculating relevancy to match queries and rank results.