This document discusses Web 2.0 and its impact on teaching and learning. It begins with definitions of Web 2.0 from various sources, noting that it allows for greater participation and sharing compared to earlier versions of the web. It then discusses how Web 2.0 tools like wikis, blogs, social networking, and videos can support constructivist learning approaches. However, it also notes that many teachers are reluctant to use new technologies. The document provides several examples of using Web 2.0 tools in physics classes and concludes with a brief discussion of potential future developments like Web 3.0.