Web 2.0 was the next step in webpage evolution. If Web 1.0 consisted of static information, Web 2.0 held a focus on user-generated content, responsive design and ease-of-use.
Examples include social media sites, which are populated with user-generated content and form a feeling of community and inclusiveness. I think of Twitter as the quintessential Web 2.0 site, mainly because of its slim timeline, which lends itself to accessibility on many platforms.
A common thread that contrasts Web 2.0 with Web 1.0 is the importance of active use instead of passive use. Web 1.0 is akin to an advanced, faster phone book. Users seek information, and have little additional use for the web page beyond that. Now, users might stay on only a handful of websites as digital citizens, being exposed to new information constantly in the form of timelines and feeds.