I believe the WYSIWYG (What you see is what you get) editor was the greatest breakthroughs in Web 2.0 since it empowered individual with no knowledge in HTML to be able to publish content on the web. In the picture above you see some of the main features of Blogger's WYSIWYG editor.
The “Web2.0″ pronounced “Web Two point Oh”: can be used as an adjective, noun, verb, adverb to describe a new technology, paradigm, and revolution. Web 2.0, a retronym, can be best described in contrast to Web 1.0, a new label since the existing label “Web” has become inadequate. Web 1.0 can now be distinguished as mostly flat, two-dimensional, and filled with read-only content. By contrast, Web 2.0 is characterized as being highly interactive, having a rich graphical user experiences, leveraging the long tail, harnessing collective intelligence, and tapping the wisdom of the crowds through opening of the web to read and write (O’Reilly, 2007). Classic examples of Web 2.0 sites and services that focus on user generated content are YouTube for videos, Digg for news, Flickr for photos, and Wikipedia for encyclopedia articles. Below is a collection of resources and research to assist you in joining in the new web.