Off-page SEO is important for ranking websites and involves factors outside a website like links, social media activity, and brand mentions. It helps search engines understand a website's quality, authority and trustworthiness. The document discusses various off-page factors like links, social profiles, reviews and directories. It provides best practices for link building through quality content while avoiding black hat techniques. Social media is also important for SEO and the document outlines common mistakes like ignoring off-page work or only sharing other's content without routing back to one's own website.