In the early days of the internet, websites were static. People would only see content uploaded by the person running the website and not anything new. These websites were referred to as a static website. Even today, most business websites we see are actually static.
Web 2.0 referred to a marked shift in the way websites were run. Web 2.0 websites are known to be dynamic and dependent on user-generated content. Social media platforms like Facebook and Twitter are, in essence, web 2.0 channels.
Web 2.0 websites make for a great place to create backlinks. Since they allow user-generated content to be published, they can be used to build backlinks. As a link building technique, it is a novel way to build a solid portfolio of backlinks based on content.
List of Web 2.0 Submission Websites