What defines a Web 2.0 application?

A Web 2.0 application is characterized by its interactivity, allowing users to not only consume but also create and share content. This participatory nature of Web 2.0 encourages collaboration among users, which can happen through features like social networking, wikis, and blogs. Unlike the earlier static websites that simply displayed content without user interaction, Web 2.0 applications focus on user engagement and community-driven content generation. This transformation signifies a shift from a one-way communication model to a more dynamic, user-generated content approach, making the application more versatile and user-friendly.

The other options represent different concepts: static websites do not offer the interactive features essential to Web 2.0; security applications focus on safeguarding transactions rather than encouraging collaboration; and platforms dedicated to online advertising do not inherently emphasize user interaction or content sharing.