This document defines Web 2.0 and social networking sites, and discusses blogs. It explains that Web 2.0 allows users to collaborate and share information online in new ways. Blogs are online journals that people frequently update with whatever they want to write. Social networking sites help create online communities where users can chat, share photos and videos, and communicate. While social networking provides benefits like free communication and information sharing, it also poses risks like oversharing private information and online bullying.