The key difference between a widget and a Web application is portability. Widgets are applications that can function on any site that accepts external content, including social networks, Blog platforms, start pages (i.e. MyYahoo), desktop platforms or personal Webpages. Widgets can be built to function differently on each platform, delivering varying degrees of integration with a social network, from accessing and using social data to not interacting with the platform at all. Social applications encourage connectivity, self-expression or collaboration, often through games, productivity tools or interactive content. (See Web Applications).