Essentially, Web 2.0 is a more socially interactive way of using the Internet. Thus, using appropriate "social software", users can share videos, music, photos, ideas and knowledge. Many users and networks use Web 2.0 technology for entertainment purposes, but there are many serious applications as well. The importance of social software for education and development is that it gives individuals and communities the ability to self-publish and also collaborate in social learning and social action projects.
More on Web 2.0.