Web 2.0 was coined in 2005 by Tim O'Reilly and focuses on allowing users to create and share content. It is characterized by user-generated content, openness, and network effects. While it enables social media marketing and engagement, it also presents challenges like information overload and unreliable content from fake accounts and spammers. Open data in Web 2.0 requires building intelligence to make sense of information and knowledge. The technologies behind Web 2.0 include AJAX, REST, lightweight programming, and APIs accessible through browsers. It also enables more collaborative online learning where students actively participate and share knowledge.