What is the Web 2.0 term means?

The term “Web 2.0” defines a set of principles and practices for web applications, which, when followed, entitle a web application to wear the Web 2.0 crown.
A web site can claim to be a Web 2.0 site if it:

• Allows users to control data presented on the web site
• Presents a platform that enables the mixing (or mash-up) of technologies and data
• Enables services to be consumed that are beyond the boundary of the application
• Harnesses collective intelligence by enabling the following:

1 - Aggregation of relevant content from hetero generous sources.
2 - User contributed content.
3 - User moderation of content via tagging and rating.

• Uses state-of-the-art technologies that take interactivity on the Web to the next level by use of popular technologies like Ajax, Flash, and Silver light.

Drop things, being a web portal, allows a user to control what the user wants to put on the page. The widget architecture allows mash up of technologies in the form of widgets. It exposes web services that external entities can consume.

The portal aggregates content from many different sources, such as photos from Flickr, news from CNN, weather reports from Weather.com, and many more. It supports user submitted content aggregation in the form of RSS feeds.

Finally, it pushes interactivity on the Web to the next level by using Ajax technologies.

Source: https://www.nilebits.com/blog/2009/11/what-is-the-web-2-0-term-means/