Page rank measures the quality and importance of websites, with higher page ranks indicating more important sites. Page rank is influenced by the number and quality of links from other sites, with links from more important sites carrying more weight. Off-page SEO involves obtaining relevant links from other sites to improve page rank and rankings. Key aspects of off-page SEO include analyzing link quality, developing a link acquisition strategy like linkbaiting, and ensuring link profiles look natural with varied and relevant inbound links from many sites. Social media is also important for SEO as it allows increasing traffic and obtaining backlinks while building an online community and brand.